A Revised Lake Trout Rehabilitation Plan for Ontario Waters of Lake Huron. Upper Great Lakes Management Unit - Lake Huron

Transcription

1 A Revised Lake Trout Rehabilitation Plan for Ontario Waters of Lake Huron Upper Great Lakes Management Unit - Lake Huron

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3 Upper Great Lakes Management Unit, Lake Huron Office MR-LHA- A Revised Lake Trout Rehabilitation Plan for Ontario Waters of Lake Huron May 4, 2012 Ontario Ministry of Natural Resources Upper Great Lakes Management Unit, Lake Huron Office 2

4 2012, Queen s Printer for Ontario Printed in Ontario, Canada Upper Great Lakes Management Unit, Lake Huron Office Ministry of Natural Resources th Avenue East Owen Sound, Ontario N4K 2Z1 (519)

5 TABLE OF CONTENTS LIST OF FIGURES... III LIST OF TABLES... III INTRODUCTION... 1 WHY REHABILITATE LAKE TROUT?... 2 OVERVIEW OF PAST REHABILITATION EFFORTS... 3 SYNOPSIS OF PROGRESS TOWARDS LAKE TROUT REHABILITATION IN ONTARIO WATERS... 5 REVIEW OF THE 1996 PLAN... 7 A REVISED GOAL AND OBJECTIVES FOR LAKE TROUT REHABILITION... 8 GOAL... 8 OBJECTIVES... 8 Short-term Objective...10 Mid-term Objective...10 Long-term Objective...11 REHABILITION STRATEGIES REHABILITATION ZONES Zone Definition...12 Zone Classification...14 STOCKING Stocking Density...17 Stocking Strains...17 Size and Age at Stocking...18 Marking...19 Other Stocking Strategies...19 EXPLOITATION CONTROL Commercial Fishery Management...20 Recreational Fishery Management...21 CONSERVATION OF REMNANT STOCKS PROGRESS EVALUATION EVALUATION CRITERIA Age Structure...24 Lake Trout Survival/Mortality...24 Spawning Stock Size...25 Natural Reproduction...26 Abundance...26 ASSESSMENT TACTICS i

6 ECOSYSTEM CONSIDERATIONS AND RESEARCH HABITAT COMMUNITY INTERACTIONS Sea Lamprey...31 Prey Species...31 Critical Life Stages and Thiamine Deficiency Complex...32 RESEARCH CONCLUSION REFERENCES ii

7 LIST OF FIGURES Figure 1. Lake trout stocking history for Canadian waters of Lake Huron, 1976 to Figure 2. Lake trout rehabilitation zones defined using a 5-minute grid system in relation to LTRZ boundaries as presented in OMNR (1996)...5 Figure 3. Lake trout rehabilitation timeline based on stocking, growth and the maturity rate of lake trout stocked in Lake Huron....9 Figure 5. Decision tree for UGLMU lake trout assessment projects Figure 6. Flowchart describing a management decision model and recommended actions as rehabilitation objectives are achieved LIST OF TABLES Table 1. Description of Lake Trout Rehabilitation Zones for Lake Huron, priority ranking and rehabilitation status and objective achieved for each zone (as of 2010 according to the 1996 Plan)...16 iii

8 INTRODUCTION This document presents an updated and revised approach for rehabilitation of lake trout (Salvelinus namaycush) populations in Ontario waters of Lake Huron. Lake Huron hereafter refers to Ontario waters of all three basins of the lake (the main basin, North Channel and Georgian Bay, Figure 4) unless otherwise specified. This document builds on past lake trout rehabilitation efforts for Lake Huron described in Argyle et al. (1991), OMNR (1996) (hereafter referred to as the 1996 Plan), Ebener (1998) and most pertinent, the recent review of rehabilitation efforts in Ontario waters (hereafter referred to as the Review) (OMNR 2009). This revised plan provides an assessment of progress towards lake trout rehabilitation in Lake Huron since the 1996 Plan was released, and will present a modified approach for rehabilitation efforts based on a critical review of the 1996 Plan presented in OMNR (2009). To clarify, the term lake trout rehabilitation will continue to be defined as re-establishment of lake trout populations that, through natural reproduction, can sustain themselves under controlled exploitation as was defined in the 1996 Plan. This plan proposes a revised goal and objectives that more accurately reflects the influences of stocking on rehabilitation timelines. Strategies to rehabilitate lake trout including the continued use of Lake Trout Rehabilitation Zones (LTRZs), various stocking related actions and means to control exploitation rates will be described. Criteria for evaluation of progress towards rehabilitation as well as tactics to gather data in support of these criteria will be presented. Ecosystem influences on lake trout rehabilitation such as sea lamprey (Petromyzon marinus) control, exotic species, and research will also be discussed. Lastly, stocking, assessment and management needs for each rehabilitation zone will be outlined in Appendix A in an effort to provide clear, specific direction for the future. 1

9 WHY REHABILITATE LAKE TROUT? Some stakeholders continue to challenge the importance that resource management agencies have placed on lake trout rehabilitation in the Great Lakes. Knuth et al. (1995) noted that in most cases, resource management staff on the Great Lakes believed that lake trout rehabilitation is a priority activity for their agencies. However, Clark and Huang (1985), Eshenroder (1987), Kernen (1995), Krueger et al. (1995a), Lange and Smith (1995) and Pister (1995) all describe the tension between agency focus on lake trout and how this often conflicts with what some stakeholders desire from Great Lakes fish communities. These differences in perspectives regarding lake trout rehabilitation highlight the potential conflict between the desire to satisfy human needs, desires and wants versus managing for ecological structure and function (Lange and Smith 1995). These different views are most often termed as utilitarian versus evolutionary-ecological land ethics, respectively (Callicot 1991; Pister 1995). These different perspectives are still found on Lake Huron today. However, sound biological reasons exist for lake trout rehabilitation in Lake Huron. For instance, lake trout inhabit a wide range of depths at different times of the year, feed on a diverse array of prey types, and exert influence as a predator across the food web (Martin and Olver 1980; Ryder and Edwards 1985; OMNR 1996; Bronte et al. 2008). This is in contrast to Chinook salmon, that fed almost exclusively on alewife and smelt (Diana 1990) and have consequently suffered precipitous declines throughout Lake Huron following the apparent collapse of the prey fish community (Riley et al. 2008). In addition, since lake trout do not rely on streams for spawning they are not as vulnerable as stream spawning species to inaccessible and/or degraded tributary habitat. Lastly, and perhaps most importantly, the diversity in lake trout forms that were present in the Great Lakes prior to their collapse indicates that the species were well suited to the Great Lakes environment and had adapted to all portions of the ecosystem (Eshenroder et al. 1995a; 1995b). Ultimately, lake trout are believed to play an important role in fish community ecology (Ryder and Edwards 1985). In addition to this biological rationale, it appears that the Lake Huron fish community cannot support large numbers of Chinook salmon as it did in the past. The collapse of the prey fish community (Riley et al. 2008) and related declines in Chinook salmon abundance (Johnson et al. 2010) highlight this fact. Although other non-native salmonids such as brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) are popular in the recreational fishery, they have never been as abundant as Chinook salmon (OMNR unpublished data). As well, these species are not expected to occupy the same dominant position in the fish community as Chinook salmon once did given that brown trout are generally accepted to be a nearshore species (Johnson and Rakoczy 2004) and rainbow trout consume large numbers of insects rather than prey fish (United States Geological Survey, unpublished data). As a result, few alternatives are likely, other than lake trout, for establishment of stable populations of a top predator in the open waters of Lake Huron. Cultural and ethical reasons also exist in support of lake trout rehabilitation efforts. Prior to the collapse of lake trout in Lake Huron, lake trout supported a large, viable fishery (Hile 1949; Baldwin et al. 1979). When rehabilitated, lake trout may again support attractive fisheries. Compelling evidence also exists that the Great Lakes supported the world s most diverse 2

10 assemblage of lake trout ecotypes and that rehabilitation of this community with lake trout as the dominant predator is a legacy that deserves attention (Eshenroder et al. 1995a). Although some stakeholders are opposed to stocking of lake trout in the Great Lakes, other stakeholders support the intrinsic value of native species such as lake trout (Krueger et al. 1995). Recent surveys also indicate that there is indeed public support for native species rehabilitation (including lake trout) (Hunt et al. 2010). Provincial policy direction and international plans have been developed to address lake trout rehabilitation due to biological and cultural/ethical reasons. In Ontario, lake trout rehabilitation is compatible with the ecosystem and ecological sustainability approaches discussed in the Strategic Plan for Ontario Fisheries (SPOF 2) (OMNR 1992), Our Sustainable Future (OMNR 2005a, 2011b), and Ontario s Biodiversity Strategy (OMNR 2005b, 2011a). In an international context, rehabilitating lake trout is a key priority for the Great Lakes Fishery Commission (GLFC) as outlined in the Strategic Vision of the Great Lakes Fishery Commission for the First Decade of the New Millennium (GLFC 2008). Lake trout rehabilitation also follows the ecosystem and ecological sustainability approaches outlined in the Joint Strategic Plan for Management of Great Lakes Fisheries (GLFC 2007). In a Great Lakes wide context, lake trout rehabilitation is identified as an important activity on Lake Superior (Hansen 1996), Lake Michigan (Bronte et al. 2008; Dexter et al. in press), Lake Erie (Markham 2008) and Lake Ontario (Stewart et al. 1999). Lastly, rehabilitation of lake trout is one of the key objectives outlined in the Fish Community Objectives for Lake Huron (DesJardine et al. 1995). As a whole, rehabilitation of lake trout is supported by strong biological and ethical rationale. OVERVIEW OF PAST REHABILITATION EFFORTS Lake trout were historically the top coldwater predator in Lake Huron. They supported large fisheries and represented a significant proportion of commercial landings (Hile 1949; Baldwin 1979). The invasion of sea lamprey, in combination with over-exploitation, caused lake trout populations in Lake Huron to collapse in all but two isolated locations (Iroquois Bay (Appendix A, Figure 5) and Parry Sound (Appendix A, Figure 6)) by 1960 (Coble et al. 1990; Eshenroder et al. 1992; Eshenroder et al. 1995b). The collapse of lake trout prompted management agencies around the Great Lakes to undertake rehabilitation efforts for this species starting in the 1940s (Eshenroder 1987). Initially the focus was on rehabilitative stocking of lake trout and early attempts at sea lamprey control which met with limited success (Hansen et al. 1995; Hansen 1999). The magnitude of the loss of lake trout in all the Great Lakes was at a level that required the need for international coordination. As a result, the GLFC was formed to direct sea lamprey control and to coordinate research on an international basis on the Great Lakes (Eshenroder et al. 1992). The role of the GLFC was further refined by the Joint Strategic Plan for Management of Great Lakes Fisheries that was first implemented in 1981 and revised in 1997 (GLFC 2007). Since the Joint Strategic Plan was implemented, lake trout rehabilitation has been a primary focus of Great Lakes resource agencies including those working on Lake Huron. Guidance for management and research activities on Lake Huron has been provided by Argyle et al. (1991), OMNR (1996) and Ebener (1998), among others. Sea lamprey control, as coordinated by the 3

11 GLFC, lake trout rehabilitative stocking, harvest controls and sanctuary creation (i.e. aquatic protected areas) have been the predominant management approaches used by the State of Michigan and the Province of Ontario to date. In the Ontario waters of Lake Huron, rehabilitative stocking started in 1969 with the stocking of splake, an early maturing hybrid of lake trout and brook trout (Salvelinus fontinalis) (Spangler and Berst 1976). The hope was that splake would be able to mature and reproduce prior to enduring the high sea lamprey induced mortality suffered by larger, older lake trout. Little evidence of splake reproduction led to the infusion of more lake trout genetic material into fish stocked in the 1980s and early 1990s by crossing splake with pure strain lake trout; these fish were referred to as backcross (OMNR 1990). With reductions of sea lamprey abundance and associated wounding rates, as well as the continued lack of reproduction from stocked backcross, the decision was made to stock pure strain lake trout after 1995 (Figure 1). Figure 1. Lake trout stocking history for Canadian waters of Lake Huron, 1972 to Following the decision to stock pure strain lake trout and to respond to the findings and recommendations of the International Conference on Lake Trout Restoration in the Laurentian Great Lakes (Selgeby et al. 1995), OMNR published the Lake Trout Rehabilitation Plan For Lake Huron (Canadian jurisdiction) (OMNR 1996). This document, which was consistent with international efforts, also provided clear direction and details for lake trout rehabilitation in Ontario waters. The 1996 Plan included the establishment of goals and objectives, specific strategies, and tactics, which included a clear focus on stocking pure strain lake trout, and the use of Lake Trout Rehabilitation Zones (LTRZs). Sixteen LTRZs were identified in the 1996 Plan (Figure 2) and were the focus for stocking, assessment and in some cases, management changes to reduce lake trout mortality. The 1996 Plan also recognized the need for regular reviews of progress towards goals and objectives. Since 1996, the Upper Great Lakes 4

12 Management Unit (UGLMU) has been implementing the basic direction provided by the 1996 Plan in efforts to rehabilitate lake trout. Figure 2. Lake trout rehabilitation zones refined from the original lake trout rehabilitation zone boundaries, as presented in OMNR (1996), using a 5 minute grid system. SYNOPSIS OF PROGRESS TOWARDS LAKE TROUT REHABILITATION IN ONTARIO WATERS To follow through on the commitment to review progress, the Upper Great Lakes Management Unit (UGLMU) of the OMNR completed a large scale examination of rehabilitation efforts (OMNR 2009). This Review was conducted in two parts: an examination of progress in each LTRZ using the goal, objectives, strategies and criteria set forth in the 1996 Plan; and a review of the 1996 Plan which will form the basis of this document, a revised rehabilitation plan for Lake Huron. Using the 1996 Plan objectives and evaluation criteria as benchmarks, progress towards rehabilitation in each of the 16 LTRZs was evaluated up to 2006 in the Review. With some exceptions, age distributions were truncated in most LTRZs with few fish observed older than six years of age. As a result, most LTRZs had not achieved the short term objective set forth in the 1996 Plan. Sources of mortality varied across the lake and included high sea lamprey 5

13 induced mortality in the North Channel (LTRZs 1 and 2) and fishing related mortality in LTRZs 7-9, 11, and The status of lake trout in LTRZs 10 and 12 was uncertain given that proportions of unclipped fish in these zones were over 20% during the latter years in the review period, but age distributions remained truncated with few mature fish observed. These results suggested that adult mortality was an impediment to rehabilitation in many parts of Lake Huron. This theory is further supported by evidence of progress in Parry Sound, Owen Sound Bay, Six Fathom Bank and South Bay where adult mortality has been controlled. For example, the Parry Sound remnant lake trout stock was successfully rehabilitated. Further, natural reproduction was observed in Owen Sound Bay (LTRZ 10; Appendix A, Figure 10), Six Fathom Bank (LTRZ 16; Appendix A, Figure 16) and South Bay (LTRZ 15; Appendix A, Figure 15). In addition, South Bay had likely reached the mid-term objective as described in the 1996 Plan by 2006 and Frazer Bay (LTRZ 3; Appendix A, Figure 3) exhibited a growing population with wild fish observed in recent fishery independent surveys and was also close to achieving the short term objective in 2006 (OMNR 2009). Excessive adult mortality may not have been the only impediment to lake trout rehabilitation. The Iroquois Bay (LTRZ 5) remnant population had not recovered despite the implementation of restrictive management actions. Additionally, in a number of LTRZs that are located in areas with few sources of adult mortality, rehabilitation did not appear to have advanced. These include Grand Bank (LTRZ 4; Appendix A, Figure 4) and the Limestones reef complex (LTRZ 7; Appendix A, Figure 7). Generally, these areas had low sea lamprey density and little or no exploitation due to their distance offshore. It is unclear why Iroquois Bay has not recovered, but for these other areas, their remoteness made stocking on top of lake trout spawning habitat difficult. In many cases fish were stocked long distances from spawning habitat which in hindsight, likely impeded the development of spawning stocks near these offshore spawning habitats, an impediment that Bronte et al. (2007) describe for some Lake Michigan spawning reefs. For the full description of progress in each LTRZ up to 2006, see OMNR (2009). Although the Review document provided the most complete synopsis of the lake trout rehabilitation program in Ontario waters when it was finalized in 2009, it only included data up to 2006 (OMNR 2009). Since this document was released, new evidence of natural reproduction first noted in LTRZs 3 and 12 has been mounting in these and other areas around Lake Huron. This includes both Michigan and Ontario waters (He et al. in press). These increases in numbers of wild fish are in addition to those observed in Parry Sound, Owen Sound Bay, Six Fathom Bank and South Bay as noted in the Review (OMNR 2009). This wide spread increase in numbers of wild lake trout and a perception of positive changes prompted a further review of data collected from 2007 to Using benchmarks suggested in the Review (OMNR 2009), lake trout data from 2007 to 2010 was summarized (UGLMU unpublished data). In contrast to the situation in 2006, positive changes were observed in a number of LTRZs including zones 3 (Frazer Bay), 7 (Limestone Islands), 11 (Point Clark), 12 (Western Bruce Peninsula), and 14 (SW Manitoulin Island). These include broadening age distributions, with many zones now having a number of age classes older than age four, older mean ages with many older than the mean age to maturity, total annual mortality rates below the upper threshold of 40 percent and most importantly, 6

14 proportions of wild fish (of all ages) increasing, and in some zones, meeting or exceeding the target of 50 % of the sampled fish. The Parry Sound (LTRZ 6) lake trout population remains rehabilitated and progress towards rehabilitation in LTRZs 15 (South Bay) and 16 (Six Fathom Bank) remains very positive as noted in the Review (OMNR 2009). However, impediments to rehabilitation in certain zones detailed in the Review (OMNR 2009) were still observed in the most recent compilation of data. Sea lamprey wounding rates in LTRZs 1 (Western North Channel) and 2 (Darch Islands) were often over wounds per 100 lake trout, well over the target threshold of 5 wounds per 100 lake trout. As a result, sea lamprey induced mortality is still expected to be a major impediment to lake trout rehabilitation in the North Channel. Additionally, little progress appears to have been made in LTRZ 4 (Grand Bank/Dawson Rock), 5 (Iroquois Bay), 8 (Watcher Islands) and 13 (Bruce Archipelago) since In LTRZs 9 (Nottawasaga Bay) and 10 (Owen Sound/Colpoys Bay), progress towards rehabilitation that was noted in the Review (OMNR 2009) appears to have stalled. The proportion of wild fish present in both zones has declined since 2006 as have catch rates of lake trout in fisheries independent assessment netting and the commercial fishery. Given the situation in LTRZ 8, 9 and 10, it appears that lake trout rehabilitation in southern Georgian Bay is not progressing as it is in other portions of Ontario waters of Lake Huron. This is a major concern given the focus on lake trout rehabilitation in this part of the lake, in part, through large yearly stocking events. One last, additional change that was widely observed in most LTRZs outside of Parry Sound, South Bay or Six Fathom Bank was an overall decline in total abundance. This decline in abundance is perplexing given increases in the proportion of wild fish in many of the same zones. However, these types of changes were observed on Lake Superior as lake trout rehabilitation progressed (Hansen et al. 1996) but overall abundances on Lake Superior were much higher than are currently observed in Lake Huron (He et al. in press). Despite similarities to Lake Superior, declining productivity in lower trophic levels such as phytoplankton (Barbiero et al. 2011; Evans et al. 2011), zooplankton (Barbeiro et al. 2009) and the overall prey community (Riley et al. 2008) lend much uncertainty to the current situation on Lake Huron. This decline in abundance and increase in wild lake trout production presents a confounding dilemma for managers. REVIEW OF THE 1996 PLAN In addition to reviewing progress in each LTRZ, the Review recommended changes to the approach described in the 1996 plan. Specifically, the Review examined the Goal, Objectives, Rehabilitation Strategies, Progress Evaluation, Ecosystem Considerations and Research components of the 1996 Plan. This examination of the 1996 Plan, in combination with the conclusions drawn from reviews of progress in each LTRZ, is the basis for the following Revised Lake Trout Rehabilitation Plan for Ontario Waters of Lake Huron. 7

15 A REVISED GOAL AND OBJECTIVES FOR LAKE TROUT REHABILITION Rehabilitation of lake trout continues to be an important goal on the Great Lakes (GLFC 2008) and OMNR remains committed to lake trout rehabilitation on Lake Huron (DesJardine et al. 1995; Dobiesz et al. 2005; Bence and Mohr 2008). In addition to the rationale provided earlier, the need for stable, self-sustaining top predator populations has become increasingly important now given the recent collapse of the alewife, the concomitant reductions in Chinook salmon, and the need to suppress the expansion of invasive species (Leach et al. 1999). GOAL With these concepts in mind, the following goal for continued lake trout rehabilitation efforts is: "To re-establish self-sustaining lake trout populations in Ontario waters of Lake Huron and thus allowing them to contribute to a healthy aquatic ecosystem by facilitating stability as the dominant top predator while maintaining viable populations and sustainable harvests through natural reproduction" OBJECTIVES A concept common to all lake trout rehabilitation plans (e.g. Hansen 1996; OMNR 1996; Ebener 1998; Bronte at al. 2008) for the Great Lakes is the progression from populations consisting of fish derived entirely from hatchery sources, to one that has limited natural reproduction, to one that is entirely sustained by natural reproduction (OMNR 2009). This concept is common across the Great Lakes basin as in most cases lake trout populations were extirpated and need to be re-established from hatchery origin fish. The timing of this progression depends on when stocking started. This concept can be displayed graphically as a timeline (Figure 3) (which is based on empirical data from Ontario waters of Lake Huron), and can be described using short-, mid-, and long-term objectives (OMNR 2009). These objectives describe the three stages through rehabilitation and provide measurable points in the process. The three objectives used in the 1996 Plan followed this progression with specific dates included for each objective (OMNR 1996). The review of rehabilitation activities in each LTRZ indicated that stocking started at different times in most LTRZs and that impediments to rehabilitation, such as sea lamprey induced mortality and fishing mortality, varied across the lake (OMNR 2009). These differences would be expected to alter the rate and time when rehabilitation occurred in each zone. As such, it was unrealistic to expect that each of the objectives would be achieved at the same time in all LTRZs. It is more appropriate to use objectives that reflect the influence of stocking and those that are based upon the number of years following initial stocking (OMNR 2009). 8

16 Figure 3. Conceptual lake trout rehabilitation timeline based on stocking, growth and the maturity rate of lake trout stocked in Lake Huron. Stocked fish Wild fish As is evident in the rehabilitation timeline, the development of spawning populations is of primary importance. For example the short- and mid-term objectives from the 1996 Plan are entirely focused on the creation of hatchery and wild spawning populations respectively. Given this focus, metrics that clearly indicate the presence and relative abundance of spawning stocks are important and must be compatible with field assessments to avoid any uncertainties when evaluating progress. We define a desired spawning population as having: Average catch rates in excess of 17 spawning lake trout / 305m of large mesh gill net during the spawning period (as per Selgeby et al. 1995). Minimum catch rates of 12 adult lake trout / net night in trap nets during the spawning period (as experienced in Parry Sound). Minimum catch rates of 1.3 adult lake trout / hour in short set gill nets, either on or nearby to spawning habitat or at randomly selected sites within a LTRZ during the spawning period (as experienced in Parry Sound). 9

17 These metrics are consistent with evaluation criteria presented later in this document. To reflect the influence of stocking on rehabilitation, while also considering the above catch rates, the following revised Objectives are presented. Short-term Objective The rehabilitation timeline, based on empirical data from Ontario waters of Lake Huron, suggests that measurable quantities of adult hatchery lake trout should be sufficiently abundant to produce measurable quantities of offspring 8-11 years following initial stocking of yearlings (Figure 3). This assumes that impediments to rehabilitation are negligible, that stocking rates are adequate and that assessment catch rate targets have been met (OMNR 2009). With this in mind, a revised short-term objective for each LTRZ, based on the initiation of stocking is as follows: Develop spawning populations of lake trout (as per spawning population benchmarks above) within 8 to 11 years of initial stocking of yearlings, where: a spawning population is defined as an aggregation of sexually mature lake trout, comprised of at least three different mature cohorts spawning in habitats with substrates suitable for egg deposition and rearing; the average age of mature lake trout is at least one year older than the age of first maturity (for each sex independently); a minimum of five stocking events, each of at least 2.5 yearlings per ha, have occurred in the LTRZ within an 11 year period. Mid-term Objective Assuming that females begin to spawn at age seven (as observed in Lake Huron), the rehabilitation timeline (Figure 3) suggests that the first wild lake trout yearlings could be present as early as eight years after the initial stocking. These wild offspring would then be recruited to UGLMU assessment gear as four year olds, 11 years after initial stocking. Subsequently, we would expect to observe wild fish in the spawning population 14 years after initial stocking at seven years of age (Figure 3). Again, this timeline assumes that impediments to rehabilitation are negligible, original stocking densities were sufficient, that the attainment of the short term objective is sustained and that catch rate targets have been met (OMNR 2009). A mid-term objective for each LTRZ that reflects this continued movement through the rehabilitation process, while also considering the influence of stocking, is as follows: Generate sustained and measurable natural reproduction of wild juvenile lake trout by the 11 th year following initial yearling stocking and recruitment of these wild fish to the spawning population 14 to 19 years following initial stocking, where: relative abundance continues to meet or exceed spawning abundance benchmarks; natural reproduction is confirmed by the presence of a minimum of 3 wild juvenile cohorts; 10

18 wild adults from several year classes combine to make up more than 25% of the spawning population. Long-term Objective The long-term objective presented in the 1996 Plan was lake-wide in scope and was contrary to the zone specific nature of the short- and mid-term objectives. Additionally, rehabilitation efforts implemented since the 1996 Plan was developed have been conducted on a zone by zone basis. A modified long-term objective that reflects the rehabilitation timeline, the influence of stocking, the zone-specific nature of lake trout rehabilitation and examines parameters that reflect stability is thought to be appropriate (OMNR 2009). The modified long term objective for each LTRZ is as follows: Establish self-reproducing lake trout populations characterized by stable spawning stocks, annual recruitment of wild fish, and total annual mortality rates less than 40%. To be clear, lake-wide rehabilitation is the desired end point and this long term objective is compatible with that goal, since rehabilitation in all the LTRZs is expected to facilitate the expansion of wild lake trout on a lake-wide basis (OMNR 2009). Lastly, although this plan is specific to Ontario waters, continued lake-wide coordination of lake trout rehabilitation efforts provided through the GLFC and implementing agencies such as the Michigan Department of Natural Resources (MiDNR) and United States Fish and Wildlife (USFWS) are also necessary for successful rehabilitation. 11

19 REHABILITION STRATEGIES Strategies to rehabilitate lake trout that facilitate the achievement of rehabilitation objectives can be divided into 4 categories: identification of areas in which to devote rehabilitation efforts, stocking methods, exploitation control, and sea lamprey control (OMNR 2009). Sea lamprey control continues to be an active component of lake trout rehabilitation efforts on Lake Huron although it is not within the mandate of the UGLMU. The other three strategies have been implemented in some form since rehabilitation began on Lake Huron and still remain the backbone of OMNR rehabilitation efforts. They provide the means to achieve rehabilitation objectives and will be discussed in detail. With respect to sea lamprey control, UGLMU staff work with the Department of Fisheries and Oceans (DFO) and the USFWS, through the GLFC s Lake Huron Technical Committee (LHTC) and are partners in the development of sea lamprey management plans. As such, specific goals or targets regarding the sea lamprey control program will not be made in this plan other than to advocate for continued OMNR assessment of sea lamprey marking rates and support for attainment of sea lamprey control targets set by the GLFC (OMNR 2009). UGLMU staff will continue to be involved with the Lake Huron Committee and LHTC to review the status of sea lamprey and influence future sea lamprey control decisions. The three primary rehabilitation strategies that the UGLMU implements (identification of areas for rehabilitation efforts, stocking methods, and exploitation control) will be described on a whole-lake basis. However, given the differences in stocking history, assessment needs (as a result of differing stocking histories) and management needs across LTRZs, individual rehabilitation plans for each LTRZ will also be developed (See Appendix A). This will ensure focused rehabilitation efforts with clearly defined strategies, avenues for adaptation, and means of measuring success in each LTRZ. These specifics were lacking in the 1996 Plan and often led to uncertainty when implementing year-to-year activities across the various LTRZs. REHABILITATION ZONES Zone Identification The identification of areas (rehabilitation zones) in the 1996 Plan provided a focus for rehabilitation activities. Conducting activities in these areas was expected to lead to a higher probability of success rather than implementing rehabilitation efforts across the expanse of Ontario waters of Lake Huron (Figure 4). The LTRZs identified in the 1996 Plan, centered on spawning habitat that historically supported lake trout reproduction, were thought to offer sufficient habitat to encompass home ranges (approximately 30 km), had suitable water temperatures and depths, had high water quality, had low lamprey abundance or lamprey populations that could be controlled, and sources of fishing mortality that could be managed. For the most part these conditions continue to be true for the 16 LTRZs identified in the 1996 Plan. However, more recent movement information indicates that the original LTRZ boundaries may not reflect the movement of adult lake trout and therefore the true spatial extent of home ranges (Alderstein et al 2007). Recent evidence also suggests that water shallower than 40 12

20 fathoms (73 m) more accurately reflects habitat used by lake trout strains currently stocked in Lake Huron (Ebener 1998). Lastly, the manner in which LTRZ boundaries were identified in the 1996 Plan did not reflect how spatial aspects of lake trout data (using a 5-minute grid system) were recorded in Ontario waters. As a result of these concerns, LTRZ boundaries have been modified and now encompass areas that conform to the 5 minute grid system and the 40 fathom contour line (Figure 4). Five minute grid squares with at least 50% of their surface area encompassing depths less than 40 fathoms are included in the revised boundaries for each LTRZ (Figure 4). It is also proposed that a new LTRZ (LTRZ 17) focusing on deepwater spawning habitat be added to allow for the rehabilitation of deepwater forms of lake trout thought to have existed historically in Lake Huron (Eshenroder et al. 1995a). LTRZ 10 which originally covered most of the eastern side of the Bruce Peninsula (Figure 2) has also been reduced in size to focus on Owen Sound Bay and Colpoys Bay where evidence of natural reproduction has been observed. Although the LTRZ boundaries have changed, their use is still considered a worthwhile approach as they continue to provide focus for efficient delivery of stocking, assessment and management activities. Without this focus, it is expected that rehabilitation efforts would falter given the expansive nature of lake trout habitat in Ontario waters of Lake Huron. Although lake trout may range outside of these new boundaries while foraging, lake wide harvest controls in the commercial and recreational fisheries still provide protection and lake wide assessment programs such as commercial catch sampling and offshore index gillnet surveys will provide data in these instances. 13

21 Figure 4. Revised lake trout rehabilitation zones for Lake Huron based on the 5 minute grid layer and the 40 fathom contour line. Depths deeper than 40 fathoms are indicated in dark blue. Zone Classification The 16 LTRZs identified in the 1996 Plan were given rehabilitation status and protection status designations (OMNR 1996). Rehabilitation Status reflected recognition of whether or not rehabilitation was likely attainable under proposed timelines. Each LTRZ was classified as either active or deferred. An active designation indicated the absence of any major impediment and acknowledged that rehabilitative stocking was being conducted. A deferred designation reflected the presence of major impediments such as excessive sea lamprey or fishing mortality and also indicated that stocking was not being carried out in that LTRZ. Protection class defined the degree of protection provided for lake trout through regulation and included three distinct classifications: primary (sanctuary status); secondary (enhanced exploitation control); and tertiary status (normal or modest exploitation control) (OMNR 1996). The Review of rehabilitation efforts highlighted that the rehabilitation status designation approach is still a useful as in some cases impediments to rehabilitation that existed in 1996 are still present (OMNR 2009). However, the deferred designation used in the 1996 Plan referred to stocking specifically and did not adequately indicate that standard year-to-year assessment activities such as commercial catch sampling were still being conducted in deferred LTRZs. 14

22 Lake trout have been observed to move into deferred LTRZs from stocking sites in active LTRZs; as a result data from lake trout are still available from deferred LTRZs. Data collected in these standard assessment projects have been useful in evaluating the status of lake trout in deferred zones as a result. For zones where stocking will not be conducted due to the continued presence of major rehabilitation impediments, the deferred designation will be more appropriately termed inactive as lake trout will not be stocked or targeted in lake trout specific assessment projects. However, for inactive LTRZs, any impediments to rehabilitation and any progress towards rehabilitation that may occur even though stocking will not be conducted will continue to be monitored in non-lake trout specific assessment programs (OMNR 2009). If at some time in the future conditions change, inactive LTRZs may be considered for stocking and lake trout specific assessment projects since they still possess attributes conducive to lake trout rehabilitation. The Review identified that the implementation of the protection status designations proposed in the 1996 Plan were not logistically feasible for administrative and practical reasons. A better alternative is to explicitly rank each LTRZ using a scoring system (for scoring results see Appendix C) based on attributes that are expected to promote or impede rehabilitation. The resulting ranked list (Table 1) reflects expectations for success, emphasizes the protection of remnant stocks, considers the ability to manage exploitation, and incorporates other management priorities across all LTRZs. The ranking process also helps identify priority LTRZs for stocking, assessment activities and implementation of protective regulations. With this approach, the highest scoring LTRZs will receive the highest priority in the rehabilitation process. Unlike the 1996 Plan, this approach recognizes the finite resources available for lake trout rehabilitation in Ontario waters of Lake Huron. One exception to the ranked list with respect to allocation of stocking resources is LTRZ 2 (the Darch Islands) as stocking associated with the on-going strain comparison study in this zone is slated to continue in the near future even though this zone ranks low in the priority 15

23 Table 1. Description of Lake Trout Rehabilitation Zones for Lake Huron, priority ranking, rehabilitation status and objective achieved for each zone (as of 2010 according to recent reviews). LTRZs with priority ranks 2 though 15 are those under consideration for stocking. Under Objective Achieved, an uncertain status indicates progress towards the short-term objective and future plans for continued stocking or initiation of stocking are uncertain. LTRZ 6 is rehabilitated and stocking does not need to occur as a result while LTRZs 12, 1, 16 and 17 are in-active zones and will not be stocked as a result. Maps detailing each LTRZ can be found in Appendix A. Details of the ranking criteria and process can be found in Appendix C.. LTRZ Name Basin Priority Current New Objective Number (Rank) Rehabilitation Rehabilitation Achieved Status Status 6 Parry Sound Georgian Bay 1 Active Active Long Term 5 Iroquois Bay North Channel 2 Active Active None 7 Limestone Islands Georgian Bay 3 Active Active Uncertain 3 Frazer Bay North Channel 4 Active Active Uncertain 15 South Bay Main Basin 5 Active Active Mid Term 9 Nottawasaga Bay Georgian Bay 6 Active Active None 11 Point Clark Main Basin 9 Active Active Uncertain 14 SW Manitoulin Main Basin 10 Active Active Uncertain Island 8 Watcher Islands Georgian Bay 11 Active Active None 10 Owen Georgian Bay 12 Active Active None Sound/Colpoys Bay 13 Bruce Archipelago Georgian Bay 13 Active Active None 2 Darch Islands North Channel 14 Active Active None 4 Grand Georgian Bay 15 Active Active None Bank/Dawson Rock STOCKING Western Bruce Peninsula Western North Channel Six Fathom Bank North Lake Huron Humps Main Basin North Channel Main Basin Main Basin Deferred Deferred Active Deferred In-active In-active Active In-active Stocking of hatchery lake trout remains one of the most important strategies for the rehabilitation program given the extirpation of lake trout in most of Lake Huron. However, it should be made clear that stocking rates will be reduced and eliminated when natural reproduction reaches certain thresholds (see more specific details under the natural reproduction criteria for Progress Evaluation). Stocking, stocking density, strain selection, stocking location/methods, and size and age of stocked fish are key factors that require consideration (OMNR 2009). New understanding into the significance of these factors has been gained since the 1996 Plan was developed, and new approaches to stocking have been implemented across the Great Lakes and require consideration in this revision. The factors discussed below are lake-wide in scope; however, they will be implemented on a LTRZspecific basis as described in Appendix A. Uncertain None Short Term NA (new zone) 16

24 Stocking Density Achievement of the short-term objective (the formation of adult populations of lake trout capable of producing measurable numbers of wild offspring) is heavily dependent on stocking lake trout in sufficient densities to lead to the desired spawning population levels. The 1996 Plan identified a stocking density of 2.5 yearling equivalents per hectare of habitat as a sufficient stocking density to create spawning populations although a habitat criterion was not defined. However, eight of the eleven zones that were stocked at this target density since 2000 did not achieve the short-term objective despite high initial survival of stocked fish (UGLMU unpublished data). Reid et al. (2001) suggested that the stocking density of 4.5 yearlings per hectare used in Parry Sound (the only successfully rehabilitated LTRZ in Lake Huron) was part of the reason for the successful rehabilitation of that population. Additionally, Ebener (1998) suggested that stocking densities be calculated using areas shallower than 40 fathoms given the fact that lean lake trout appear to confine themselves to these depths in Lake Huron. With these considerations in mind: Stocking densities will be targeted at 4.5 yearlings per hectare or higher based on the new LTRZ boundaries which only include depths shallower than 40 fathoms. Stocking Strains A variety of lake trout strains have been stocked in Lake Huron and include: Big Sound (Georgian Bay remnant stock from Parry Sound) Iroquois Bay (Georgian Bay remnant stock) Lake Manitou (inland lake strain from Manitoulin Island (Appendix A, Figure 3), Lake Huron) Michipicoten Island (Lake Superior strain) Slate Island (Lake Superior strain) Seneca Lake (inland lake strain from New York State) Genetic analysis of wild fish in Parry Sound, South Bay and Owen Sound suggest that Parry Sound and Lake Manitou strains have contributed most to the production of wild fish (Stott 2004). In Parry Sound, stocking yearlings produced from the remnant Parry Sound strain was one key factor to successful rehabilitation (Reid et al. 2001). These experiences have reinforced the importance of stocking strains native to the Lake Huron basin. The use of Seneca strain lake trout in Lake Huron has shown promise due to their lower sea lamprey induced mortality (Madenjian et al. 2004). This can result in higher survival and a higher probability of contributing to natural reproduction and rehabilitation in locations where sea lamprey wounding rates and associated mortality are high. Additionally, paired plant experiments have been conducted since the 1996 Plan was implemented to compare the performance of specific lake trout strains. Results from these experiments are currently being analyzed although preliminary findings suggest that Michipicoten lake trout contribute higher returns to fisheries versus the Slate Island while 17

25 Seneca strain lake trout have outperformed the Parry Sound strain in southern Georgian Bay (UGLMU unpublished data). Seneca strain lake trout also appeared to survive better to older ages than the Parry Sound strain in the same study, however mean ages for these two strains are less than five years of age. Analysis of data generated in the paired plants has also highlighted the impacts of fishing mortality, as indicated by the low mean ages of lake trout recovered in these experiments, given the apparent lack of other major sources of mortality in at least one location. As both of the current paired plant experiments (which are being conducted in LTRZs 2 and 9) have been conducted for at least eight years (the length of one generation for lake trout), stocking two strains simultaneously in these zones will be terminated. Pending analysis of the results from these experiments, changes to those strains used for future stocking will be made to maximize returns and contributions to wild recruitment. The current focus on only stocking lean lake trout strains that utilize nearshore, relatively shallow areas of the lake (Ebener 1998) ignores that the majority of lake trout habitat in Lake Huron consists of deep offshore waters which were thought to historically support deepwater forms of lake trout (Eshenroder et al. 1995a). Eshenroder et al. (1995a; 1995b) provided a compelling argument for the stocking of a variety of lake trout forms including deepwater strains. Currently the only deepwater form of lake trout available for stocking is the Klondike strain from Lake Superior. This is a deepwater form of lake trout that are also known as humpers due to their presence on underwater reefs or humps. They are currently being stocked on deep water reefs in Lake Erie, have been recommended for stocking in Lake Michigan (Bronte et al. 2008), and are a potential strain for stocking in Lake Huron (OMNR 2009). To conclude, the following considerations will be implemented with respect to stocked strains of lake trout: Lake trout strains native to the Lake Huron basin (Parry Sound, Iroquois Bay and Lake Manitou) will receive priority for stocking; Preference should also be given to those strains that are most closely genetically related to Lake Huron strains, namely Lake Superior strains; Seneca strain lake trout should be assessed in LTRZs where sea lamprey induced mortality is an impediment to rehabilitation; Finalize and incorporate results of the current paired plant experiments into future stocking activities; A deepwater lake trout strain should be stocked and assessed in LTRZ 17. Size and Age at Stocking Yearling lake trout represent the bulk of fish stocked into Lake Huron. This approach is supported by Elrod et al. (1988), Hansen (1994) and Madenjian et al. (2004) who suggested that survival of large yearling lake trout is higher than those stocked at smaller sizes and younger life stages. Yearling lake trout are also the primary age of lake trout stocked in Lake Michigan (Bronte et al. 2008) and Lake Erie (Markham et al. 2008). As a result: 18

26 Yearling lake trout will continue to represent the majority of lake trout stocked in Lake Huron. Marking The ability to identify stocked lake trout is crucial to evaluating the progress of rehabilitation efforts. For example, assessment of the proportion of unmarked (wild) lake trout as per the mid-term objective requires that stocked fish be differentiated from wild fish. Marking also allows aging of stocked fish and assessment of movement. Currently all stocked lake trout are fin clipped using a six year rotation. Approximately twenty percent of fish stocked at each stocking site are also marked with coded-wire tags (CWTs) which allow for the collection of more detailed movement, age and strain related information. However, fish must be lethally sampled to allow extraction and subsequent identification of the CWT. With respect to marking: All stocked lake trout will be fin clipped using the existing 6-year clip rotation; A minimum of 20% of all lake trout stocked in each LTRZ will be coded-wire tagged; Where coded-wire tagged fish are stocked, the UGLMU will increase targeted efforts to recover fish with coded-wire tags in assessment programs. Other Stocking Strategies Lake trout stocking in most LTRZs is conducted on a yearly basis and does not necessarily mimic natural patterns in recruitment. In fact, Dunlop and Brady (1998) and Reid et al. (2001) suggest that cessation of stocking may in fact favour the production of wild lake trout in some cases due to decreases in intra-specific competition. With this in mind, the UGLMU has been conducting pulse stocking in LTRZs 7 (the Limestone reef complex) and 8 (the Watcher Island complex). Pulse stocking consists of stocking at higher than normal rates for three consecutive years in a location followed by a three year hiatus over the course of three complete cycles. Recent work from Lake Michigan indicates that lake trout stocked in the vicinity of spawning habitat showed increased return rates as sexually mature adults to these locations (Bronte et al. 2008). Concerns of increased predation, including cannibalism, by stocking directly on shallow water spawning shoals (Jones et al. 1995), has lead the State of Michigan to stock lake trout in deeper locations in Lake Huron, offshore from spawning habitat (Johnson et al. 2004a). To date this has resulted in increased survival to adulthood (Johnson et al. 2004a) but it is unclear if these fish will form an effective spawning stock. Given these uncertainties and the importance of forming effective spawning stocks on suitable spawning habitat, stocking in the vicinity of spawning shoals is the preferred approach where possible. In an attempt to mitigate mortality of juvenile lake trout, alternative stocking strategies such as stocking at night or in deeper, offshore waters in proximity to spawning habitat will be considered since predation at the time of stocking can often be an issue (Jones et al. 1995). Based on available information stocking strategies will include: 19

27 Existing pulse stocking activities should be continued for three full cycles, evaluated, and expanded to other priority rehabilitation zones if they prove successful; Other pulse stocking alternatives may be investigated including alternate year stocking; Stocking directly on or in close proximity to spawning habitat, by boat if required, is the preferred method, particularly in the case of offshore LTRZs; Night stocking should be considered as a possible tool to reduce daytime predation by both avian and aquatic predators. EXPLOITATION CONTROL Lake trout grow slowly, mature at older ages, have relatively low reproductive potential, and have long life expectancies compared to other salmonids (Ryder and Edwards 1985; Evans and Olver 1995). These attributes make lake trout populations particularly vulnerable to overexploitation. Lake trout populations are sustainable only when mortality rates from all combined sources are relatively low (Eshenroder et al. 1995a). As a result, control of sea lamprey numbers and fishing mortality is crucial to allow for successful rehabilitation. Fishing mortality on lake trout in Lake Huron results from both commercial and recreational fishing. Lake-wide strategies to control fishing mortality from both sources will be outlined below; however, specific strategies are presented in Appendix A to clarify management actions for each LTRZ. Commercial Fishery Management Lake trout catches in the lake-wide Lake Huron commercial fishery have at times impeded lake trout rehabilitation (Eshenroder et al. 1995b). Although the impacts of the historic fishery have been debated (Coble et al. 1990; Eshenroder et al. 1992, Eshenroder et al. 1995b), it is likely that commercial exploitation contributed to the initial collapse of lake trout. Additionally, the recent reviews of data suggested that fishing mortality may be impeding current rehabilitation efforts in some areas in Ontario waters. This is suspected as sea lamprey wounding rates were low and age distributions were chronically truncated despite a long history of stocking in some LTRZs (OMNR 2009). Commercial fishing impacts lake trout rehabilitation as a consequence of their by-catch (i.e. caught but not sought) in monofilament gill nets targeting lake whitefish. This lake trout bycatch can result in high lake trout mortality (Gallinat et al. 1997). As an alternative to gill nets, commercial trap nets allow the live release of unwanted or undersized fish (Johnson et al. 2004b). Finding ways of reducing lake trout by-catch, while allowing the commercial fishery to continue is crucial to achieving successful lake trout rehabilitation. To manage the commercial fishery on Lake Huron, two primary mechanisms exist: quotas (or total allowable harvests), and conditions of fishing (implemented when commercial fishing licenses are issued). Quotas are applied spatially through the use of 17 Quota Management Areas (QMAs) and are managed on a yearly basis (Mohr et al. 1997). Licence conditions can 20

28 include limits on types of fishing effort, types or configurations of gear, as well as spatial and seasonal restrictions. Some current conditions include a minimum harvestable size of lake trout (44 cm total length (17 inches)), minimum and maximum size of gill net mesh sizes and the use of spatial restrictions such as the Grand Bank sanctuary. Permutations of all these various mechanisms are in use to minimize lake trout mortality in the commercial fishery. In the past, lake trout quotas were small and reflected incidental catches while targeting lake whitefish. As lake trout populations expanded due to intensified stocking (Figure 1), larger lake trout quotas were implemented on a lake-wide basis to reflect the increased by-catch of lake trout while maintaining mortality within acceptable limits. However, quotas do not provide protection to any specific segments of a lake trout population and do not ensure that discarded fish are reported or survive. Management of the commercial fishery on Lake Huron needs to take into account lake trout rehabilitation and should complement the stocking and management strategies within individual LTRZs. As a result the following options will be explored and potentially implemented: Maintain existing sanctuaries; Consider new sanctuaries for high priority areas; Conduct yearly reviews of lake trout quotas in relation to progress towards rehabilitation objectives; Implement reductions in quotas for other species (e.g. lake whitefish) if incidental catch of lake trout in gill nets is too high; Promote the use of alternative gear configurations that minimize incidental catch of lake trout (e.g. suspending gillnets off the lake bottom); Encourage the use of live capture gear (trap nets) throughout the lake by exploring the concept of enhanced lake whitefish quotas for fisheries using live capture gear Allow the use of both commercial gear types in low priority LTRZs, but only in the presence of additional regulatory controls; Implement seasonal exclusions from areas where lake trout spawn; Reduce commercial fishing activity in or adjacent to lake trout rehabilitation zones where fishing mortality is excessive. Sport Fishery Management Prior to the recent decline in the Chinook salmon sport fishery (Bence et al. 2008), lake trout were not often targeted on a wide scale by the sport fishery, although localized open-water and winter ice-fisheries have provided some harvest in the past (Reid et al. 2001). However, popular local sport fisheries for lake trout in confined LTRZs such as Parry Sound and Iroquois Bay have the ability to impede rehabilitation (Reid et al. 2001; Liskauskas 2002). Additionally, the cumulative effects of harvest from the sport and commercial fisheries along with sea lamprey induced mortality can inhibit rehabilitation at lake-wide and local levels. As a result, regulating the sport fishery, in concert with sea lamprey control and commercial fishery regulation, is necessary. 21

29 Managing the lake trout sport fishery harvest can be accomplished by a number of methods. These include seasonal closures, sanctuaries, catch and possession limits, size limits and selective harvest strategies such as no-wild-fish-harvest regulations. Lastly, catch-and-release regulations such as those in Parry Sound (Reid et al. 2001) can allow fishing to continue but limit mortality. Some of these strategies are already in place at certain locations in Lake Huron and may be expanded. A lake-wide sport fishing closure for lake trout from September 30 th -January 1 st is currently in place and possession limits were recently reduced from three fish to two fish. Sizebased (maximum size limits) and catch-and-release regulations are also in place in Parry Sound (LTRZ 6) and Iroquois Bay (LTRZ 5). Additionally, a no-wild-fish-harvest strategy is employed in Iroquois Bay. LTRZ 4 is the only true sanctuary (closed to all sport and commercial fishing) specifically created to protect lake trout although other lake trout sport fishspecific closures exist. Continued use and expansion of these approaches is advocated as follows: Maintain existing sanctuaries; Create new sanctuaries in high priority areas; Implement protective size limits to facilitate rehabilitation; Maintain current closed season in all LTRZs; Consider closed winter seasons (Sept 30 th to May 1 st ) where winter exploitation is considered excessive; Reduce bag limits to one or no lake trout in rehabilitation zones with limited spawning stock biomass (i.e. Iroquois Bay); Expand the use of size-based regulations where appropriate; Apply a no-wild-fish-harvest regulation where natural reproduction of lake trout is evident and the long term rehabilitation objective has not yet been achieved; Educate anglers in proper lake trout catch-and-release techniques; Encourage the use of terminal tackle that facilitates successful catch-andrelease. CONSERVATION OF REMNANT STOCKS Two remnant populations, Parry Sound and Iroquois Bay, avoided extirpation in Lake Huron and are the last of the 12 reported varieties of lake trout that inhabited Lake Huron (Loftus 1980). Given their long evolutionary history and local adaptation these populations are important to lake trout rehabilitation and brood stocks have been developed from both sources. These strains are currently being stocked in a number of LTRZs throughout the North Channel and Georgian Bay (OMNR 2009). The Parry Sound population was rehabilitated through extensive regulation of the sport fishery, rehabilitative stocking, and the absence of commercial fishing (Reid et al. 2001). In contrast, the Iroquois Bay spawning population has not recovered from low levels of abundance despite continuing survival of stocked fish. Although production of wild juveniles has been observed, this appears to have declined in recent years and additionally, 22

30 recruitment of wild or stocked fish to the spawning population appears to be negligible. This may be as a result of intra-specific competition as Iroquois Bay has been stocked at very high densities (7.5 yearlings/ha) since 1995 (OMNR 2006). A reduction in stocking densities to half the new target of 4.5 yearlings is likely necessary to reduce competition between stocked and wild lake trout. As such, Iroquois Bay has not achieved the short term objective (OMNR 2009). From the Parry Sound and Iroquois Bay experiences, conservation strategies for remnant stocks are limited to developing brood stock for rehabilitative stocking and minimizing, or even eliminating, fishing mortality from both commercial and recreational sources. Both Parry Sound and Iroquois Bay have been classified as active, high priority LTRZs. These two important LTRZs will be managed in the following way: Manage Parry Sound in a highly conservative manner to maintain harvest levels below 0.33 kg/ha (Reid et al. 2001); Close the recreational fishery in Iroquois Bay until the mid-term objective has been achieved. Continue to stock Iroquois Bay as required, however reduce stocking densities to 2.25 yearlings/ha. 23

31 PROGRESS EVALUATION Integral to lake trout rehabilitation is a means to evaluate progress towards the objectives. The 1996 Plan provided eight evaluation criteria to measure progress; these included total annual mortality limits, rates of natural reproduction and spawning stock size among others. However, some of the criteria included in the 1996 Plan were difficult to measure or were too general (OMNR 2009). The ability to measure progress towards objectives is very important; hence the revised evaluation criteria presented here are in the form of directly measurable indicators. EVALUATION CRITERIA Age Structure The 1996 Plan stated that the age structure of lake trout populations in each LTRZ should be multi-aged with the mean age of the spawning population at least one year older than the mean age of first maturity. While originally presented as a single criterion called Age Structure, it is clear that this included two distinct criteria: multiple ages should be present in the population, and a substantial proportion of the population should be mature and contributing to reproductive potential (OMNR 2009). These conditions continue to be important evaluation criteria that are easily calculated and provide a clear indication of progress towards rehabilitation. As all the Rehabilitation Objectives are focused on the creation and maintenance of spawning stocks (which necessitate the presence of multiple year classes of old (age 6+), sexually mature fish), the assessment of age structure is extremely important to evaluate progress. To expand on the criteria presented in the 1996 Plan, the mean age of the spawning population needs to be much older than the mean age to maturity. It is suggested that at least seven age classes, older than age four (the age when full recruitment to assessment gear occurs), be represented in lake trout populations across Lake Huron. As lake trout generally mature between ages six and eight, representation of seven age classes in an assessed population would indicate the presence of numerous, mature cohorts in a population meeting this target (OMNR 2009). It is recognized that the presence of additional older year classes is desired and is expected as rehabilitation progresses. The age structure of the population in conjunction with spawning stock size is the primary criteria for assessing progress toward lake trout rehabilitation. The original Age Structure criteria from the Plan will now be considered as two distinct criteria: The population should be multi-aged with a minimum of seven year classes present older than age four; As a minimum, the mean age of the spawning population should be at least one year older than the mean age to maturity. Lake Trout Survival/Mortality The 1996 Plan recommended an upper total annual mortality threshold of 40%. This is still a useful criterion to be used when evaluating lake trout population status. Although Statistical 24

32 Catch-At-Age (SCAA) models (Quinn and Deriso 1999) can be used to partition various sources of mortality and help direct management measures, catch curves (Ricker 1975) are still the most common method the UGLMU uses to generate mortality estimates. This is a result of the data and workload intensive nature of developing and using SCAA models. While using catch curves a minimum of five fully recruited age classes are required for catch curve mortality estimates (OMNR 2009). Caution should be exercised to ensure that the restrictive assumptions of catch curves mortality estimates are satisfied (e.g. constant stocking and/or recruitment rates). The following will be implemented with respect to lake trout mortality rates: Total annual mortality should not exceed 40% in active rehabilitation zones; A minimum of 5 year classes will be used for estimating mortality from catch curves (Ricker 1975). Spawning Stock Size The establishment of a spawning stock is integral to achievement of the short- and mid-term objectives and the 1996 Plan presented one metric for evaluation of this criteria: CPUE of spawning lake trout per 305m of large mesh gill net as per Selgeby et al. (1995). This is still a very useful indicator; however other metrics exist to estimate reproductive potential. These include Statistical-Catch-At-Age (SCAA) models (Quinn and Deriso 1999) that provide preliminary estimates of spawning stock size and other metrics of reproductive potential such as spawning potential ratio (SPR) (Clark 1991; 2002). These are already being used in U.S. waters of Lake Huron (Sitar et al. 1999). In addition, experience at the UGLMU using non-lethal netting techniques such as trap netting and short-set gill netting in LTRZs such as Parry Sound has identified that catch rates from these netting methods can also be useful in determining if spawning populations are present (Reid et al. 2001). Mark and recapture methods can also be used to generate population estimates using non-lethal techniques (Ricker 1975). One caveat regarding targets for abundance metrics that has emerged recently is that declines in overall productivity levels in Lake Huron lend some uncertainty to the continued applicability of abundance targets developed prior to 2004, particularly in the face of declines in lake trout abundance that have been observed since However, regardless of how spawning stock size is estimated, it should be reiterated that efforts to estimate spawning stock parameters should be predicated on attainment of the age structure criteria and low annual mortality. Based on the discussion in the Review, the following metrics and additional considerations will be used to determine if spawning stocks of sufficient size exist: Average catch rates of 17 spawning lake trout / 305m of large mesh gill nets in the fall; Minimum catch rates of 12 adult lake trout / net night in trap nets set near spawning reefs in the fall; Minimum catch rates of 1.3 adult lake trout / hour in short-set gill nets; 25

33 Use age structured models to estimate spawning stock size and assist in determining biologically meaningful quotas where sufficient data exists; SPR values should be calculated and maintained above 0.33 where sufficient data exists; Use mark-recapture methods for estimating spawning stock size where possible. Natural Reproduction Evidence of natural reproduction represents one of the primary indicators of progress towards the mid-term objective. The 1996 Plan recommended that when 50% of age-two fish observed in a LTRZ were unclipped, stocking should be reduced or terminated. However, age-two fish are rarely observed in typical assessment programs and this criterion provides no guidance with respect to sample size or number of observations of wild fish of this age. Ebener (1998) suggested that catches of one or two wild juveniles per 305m of gill net indicates progress towards the mid-term objective; experience in Parry Sound (LTRZ 6) and South Bay (LTRZ 15) confirms the utility of this approach in Ontario waters. Ebener (1998) also suggested that stocking should be reduced when wild fish comprise 25% of the mature portion of a population. Additionally, experiences in Parry Sound (Reid et al. 2001) and in inland waters of Ontario (Dunlop and Brady 1998) suggest that stocking should be terminated when natural reproduction increases, presumably above 25%. In an effort to provide clarity for this important criterion, the following measures will be used: Catches of 2 or more unclipped juvenile fish per standard UGLMU index net indicate successful reproduction and natural recruitment; When target assessment CPUE rates are achieved and 25% of the spawning population is unclipped, stocking plans should be reviewed; Stocking should be reduced or terminated once 50% of a population, that already satisfies the spawning stock biomass criteria, is unclipped in two consecutive years of netting surveys. Abundance The 1996 lake trout rehabilitation plan noted that lake trout abundance should increase as rehabilitation progressed. However, the original recommendation provided no guidance on how to quantify progress towards this goal, particularly with respect to the abundance of the population as a whole. The plan did provide some criteria for specific segments of the population such as spawning stock size (i.e. abundance of spawning aged fish on spawning reefs) and the abundance of wild juveniles, and set out criteria for these metrics associated with specific rehabilitation objectives. A target or threshold to measure overall lake trout abundance was not provided. Furthermore, the collection of relative abundance measures on spawning reefs in the fall has proven to be difficult, if not impossible, in many of the more exposed, offshore LTRZs (such as LTRZ 4, 7 and 8). To address these short comings, the 'Abundance' metric proposed here is thought to reflect the abundance of fish (of all ages) that are fully recruited to index fishing gear at times of the year when assessment is possible, and is intended to complement those criteria that target specific segments of the population. While similar indicators of relative abundance are available from a number of sources 26

34 including catch-per-unit-effort (CPUE) from commercial or recreational fisheries, data from the OMNR's standardized offshore index assessment program is felt to provide a more rigorous indication of overall lake trout abundance. It is important to note, that in this context, 'Abundance' is measured in terms of CPUE, and is actually an indication of relative abundance as opposed to an absolute count of individuals. The OMNR's offshore index assessment program has been implemented by the UGLMU for a number of years and provides a ready source of data for this criterion. The long time series for this survey, dating back to the 1970s in some parts of Lake Huron, provides robust benchmarks for comparisons with new areas. As well, this type of assessment survey can be more easily employed in the spring or summer (when weather and lake conditions are more stable and safe) when lake trout are not spawning and off of a larger vessel than is required for fall spawning surveys on shallow spawning habitat. Lake trout CPUE data from surveys conducted by the Lake Huron and Superior offices of the UGLMU would suggest that catches of 8-10 lake trout per net (385 m of graded mesh monofilament from 32 to 127 mm; Appendix B) in this assessment program would indicate the establishment or maintenance of a sufficiently large lake trout population to satisfy the rehabilitation objectives. Depending on the state of rehabilitation in a particular LTRZ, subsequent follow-up assessments may be warranted. It should be noted however, that uncertainty regarding the target value for this metric, similar that to for Spawning Stock Size, also exists given recent changes in Lake Huron. The following considerations provide clarity for this revised criterion: Abundance will refer to the relative abundance of lake trout of all ages captured outside of the spawning season in spring and summer assessment activity; Relative abundance estimates (CPUE) will be derived from either spring or summer assessment programs using graded-mesh gill nets; CPUE of 8 or more lake trout per offshore index net will be considered an indicator of sufficient densities of lake trout to satisfy the short term rehabilitation objective; Catch rates in the commercial and recreational fisheries should not be used to provide specific abundance criteria, although they can provide general trend information and indicate the need to initiate independent assessment surveys. ASSESSMENT TACTICS As presented in Figure 3 and discussed with respect to Objectives, lake trout rehabilitation is expected to follow a progression from development of a population and subsequent spawning stock using stocked fish, to production of wild fish through natural reproduction by stocked adults, to a population that is entirely self sustaining. Field programs and assessment tactics need to collect data that allows calculation of the evaluation criteria, which are then used to determine progress through this progression and subsequently, attainment of rehabilitation objectives (OMNR 2009). Preliminary insights into whether stocked lake trout are surviving and forming spawning populations in a LTRZ have often been provided by the commercial fisheries catch sampling program and the offshore index assessment programs conducted by the UGLMU. Although 27

35 not specifically targeting lake trout, sampling of the commercial catch and assessment of the offshore fish community via offshore index netting provide data by which to evaluate the progress of lake trout rehabilitation. These data are then used to determine when and where fishery-independent netting, targeting lake trout, is warranted. These two programs will continue to be important sources of data for lake trout rehabilitation purposes. Past fishery-independent lake trout assessments have been conducted using a range of lethal and non-lethal protocols and gear types including the offshore index netting protocol, trap nets, short-set, small-mesh gillnets and overnight sets of large-mesh gillnets on spawning shoals. Additionally, fall implementation of the spring littoral index netting (SLIN) protocol (Hicks 1999) has been used and called fall littoral index netting (FLIN) surveys. During the Rehabilitation Review it became evident that fewer and more standardized assessment protocols and gears were required to facilitate trend-through-time and spatial comparisons. As a result, future lake trout assessment efforts will be standardized using a limited suite of protocols and gear types, which will include both lethal and non-lethal protocols depending on concerns regarding lake trout mortality (i.e. the need for non-lethal netting in Iroquois Bay for instance) (Figure 5). Specifics for each of the protocols are included in Appendix B. This approach has been used to develop assessment plans (which are coordinated with stocking and management activities) for each LTRZ; these plans take into consideration the current status of rehabilitation in each LTRZ when determining future activities (Appendix A, Table 2). 28

36 Figure 5. Decision tree for UGLMU lake trout assessment projects. OSIA indicates the use of offshore index assessment projects and FLIN indicates the use of fall littoral index netting projects. 29

37 ECOSYSTEM CONSIDERATIONS AND RESEARCH Although the rehabilitation objectives do not include conditions within the wider Lake Huron ecosystem in their scope, biotic and abiotic conditions in Lake Huron can have a major influence on lake trout rehabilitation. Factors such as habitat quality/availability and interactions within the fish community can influence lake trout rehabilitation. Strategies specific to these factors are presented, as well as a synopsis of research needs specific to lake trout rehabilitation. HABITAT Habitat is not explicitly captured in any of the three rehabilitation objectives, but plays a pivotal role in rehabilitation success. Until very recently, Lake Huron open-water and spawning habitat was not thought to be limiting (Liskauskas et al 2004). However, reductions in lake levels in recent years may have an impact on the habitat available for shallow spawning lake trout. In addition, the proliferation of invasive species such as zebra and quagga mussels (Dreissena polymopha and Dreissena bugensis) may reduce spawning site quality. In 2009, MiDNR biologists began documenting rich growths of periphyton on once-pristine spawning reefs in Thunder Bay, Lake Huron, leading to concern for egg survival if oxygen levels have been reduced in the interstitial spaces of the reefs (James Johnson pers. comm.). These algae growths may be a response to redirection of nutrients to the substrate by dreissenid mussels (Hecky 2004). Round gobies (Neogobius melanostomus) and rusty crayfish (Orconectes rusticus) predation on lake trout eggs has also raised concern regarding potential impacts on lake trout reproduction (Chotkowski and Marsden 1999). Although spawning substrate in most of Lake Huron is thought to be abundant (Ebener 1998), field observations in areas of abundant habitat suggest fish utilize discrete areas for spawning and that the location of these areas may change from one year to the next (UGMLU unpublished data). It is unclear why these discrete locations are chosen in large areas of seemingly suitable habitat (Gunn 1995). As a result of the uncertainty around site selection by spawning fish, the incremental loss of habitat in certain portions of Lake Huron through shoreline development may have unknown, negative impacts on the reproductive capacity of lake trout and consequences for lake trout rehabilitation. Given these uncertainties, the following actions with respect to habitat are recommended: Document and protect from disturbance lake trout spawning sites, or sites with suitable spawning habitat, throughout Lake Huron. COMMUNITY INTERACTIONS As a post-glacial, colonizing species, lake trout are most frequently found in simple fish communities (Martin and Olver 1980). Today, numerous exotic species exist in the Great Lakes and this has had consequences for lake trout rehabilitation. In Lake Huron, the exotic species that are thought to have the most impact on lake trout include the sea lamprey (Sitar et al. 1999) and alewife (Alosa pseudoharengus) (Madenjian et al. 2008). 30

38 Sea Lamprey Sea lampreys were first documented in Lake Huron in 1937 (Berst and Spangler 1973) and sea lamprey predation has been identified as a significant cause of mortality for lake trout in most areas of Lake Huron (Johnson and VanAmberg 1995; Sitar et al. 1999). Sea lamprey predation continues to be regarded as a significant impediment to lake trout rehabilitation (Eshenroder et al. 1995a; Ebener 1998; Sitar et al. 1999). Hansen (1999) noted that lake trout populations in the Great Lakes will probably be able to rebuild in the face of either limited fishing mortality or controlled sea lamprey induced mortality, but the combined effect of both mortality sources if left uncontrolled is likely sufficient to prevent rehabilitation in some cases. Due to these concerns, the Sea Lamprey Integration Committee (SLIC) of the GLFC is currently developing lake-wide sea lamprey management plans for each Great Lake (GLFC 2009). Although implementation of sea lamprey control efforts is not within the specific mandate of the UGLMU, the following actions will be undertaken to address the continued impacts of sea lamprey predation: Continue to advocate for control programs that reduce sea lamprey abundance and ensure that marking rates are below the GLFC target of five wounds per 100 lake trout; Continue to contribute to the sea lamprey assessment program by measuring marking rates in Ontario waters of Lake Huron using standardized wound recording methods; Contribute to a Lake Huron sea lamprey management plan through participation in the Lake Huron Committee and Lake Huron Technical Committee Prey Species Historically, the diet of lake trout in the Great Lakes consisted largely of ciscos (Coregonus sp.) and sculpin species (Cottus sp. and Myoxocehpalus sp.) (Dyer et al. 1965; Christie et al. 1987; Conner et al. 1993; Owens and Bergstedt 1994), which provided lake trout with prey that allowed them to attain large sizes. From the 1950s until recently, the prey community in Lake Huron was largely dominated by exotic species including alewives, which were the major diet item of lake trout in Lake Huron (Bence et al. 2008). A diet high in alewives has been shown to contribute to Thiamine Deficiency Complex (TDC), an affliction that causes increased mortality of lake trout eggs and fry (Fitzsimmons 1995; Fisher et al. 1996). The recent collapse of alewives in Lake Huron (Riley et al. 2008) may benefit lake trout by forcing them to prey on native forage and negate TDC concerns. However, the biomass once represented by alewives in the prey community has not been replaced by other species and adult lake trout growth rates have declined as a result (Bence et al. 2008). Given the negative impacts of exotic species consumed by lake trout, and the uncertainties raised as a result, the following approaches will be given consideration: Facilitate the suppression of exotic prey species through top predator consumption; 31

39 Encourage the recovery of cisco (and related deepwater species) throughout Lake Huron by supporting the recommendations made in the Lake Huron Lake Herring Recovery Guide (LHTC 2007). Critical Life Stages and Thiamine Deficiency Complex The absence of significant natural recruitment in many parts of the Great Lakes despite the successful survival and establishment of spawning stocks of hatchery reared fish in some areas, has led scientists to suggest that conditions during early life stages are the single largest impediment to lake trout rehabilitation (Krueger et al. 1995b; Fitzsimons et al. 2002). A diet rich in alewives has been shown to cause TDC which has been implicated in a lack of wild reproduction (Fitzsimmons 1995; Fisher et al. 1996; Fitzsimmons and Brown 1998). However, the recent (2004) collapse of alewives in Lake Huron has provided clarity regarding other impacts of alewives. After 2004, the number of wild young-of-year lake trout fry observed in assessment surveys increased dramatically in many locations around Lake Huron (Riley et al. 2007). These data suggest alewife consumption of lake trout fry, as observed by Kruger et al. (1995b) and O Gorman et al. (2000) in Lake Ontario, was having a much larger impact than expected on rehabilitation in Lake Huron. Madenjian et al. (2008) discuss this phenomenon across the Great Lakes and suggest that consumption of lake trout fry by alewives is a primary impediment to rehabilitation. Recent data from Lake Huron would seem to confirm this theory with large increases in natural reproduction in many new locations since the disappearance of alewife (OMNR 2009; UGLMU unpublished data). The impacts of other exotic species such as round gobies have also been brought into question as they have been observed foraging on lake trout eggs in a laboratory environment (Chotkowski and Marsden 1999). Since the round goby invaded Lake Huron they have become more prevalent in the diet of lake trout (OMNR unpublished data) making their overall influence on lake trout unclear. With these considerations in mind, the following needs regarding lake trout early life stages exist: Evaluate rates of lake trout natural reproduction in the absence of alewives; Promote the evaluation of the effects of round goby predation on natural reproduction of lake trout through research projects; Encourage the recovery of native prey species, especially cisco; Facilitate the suppression of alewives in Lake Huron; Monitor the prevalence of TDC through yearly egg collections from spawning lake trout populations. RESEARCH Given the changes in the Lake Huron ecosystem over the last century, research continues to play an important role in lake trout rehabilitation. Uncertainty in many areas highlights the 32

40 continued need for research. Topics for research include the impacts of invasive species, changes in the prey community, habitat issues, and uncertainties regarding management decisions which stem from ecosystem change. For a more thorough discussion of these topic areas see OMNR Specific research needs that encompass these topics include: Investigate the impacts of alewives along with other impediments such as fishing mortality and sea-lamprey-induced mortality to identify impediments to lake trout rehabilitation; Investigate whether round gobies, rusty crayfish and other exotics are inhibiting lake trout rehabilitation; Assist in the verification and improvement of rehabilitation criteria; Identify impediments to lake-wide recovery of the native prey community, especially cisco; Identify the key attributes of spawning habitat that have been associated with successful natural reproduction and the characteristics that influence site selection by lake trout spawning stocks; Investigate effective management models for multi-species fisheries in Lake Huron that incorporate lake trout rehabilitation needs; Continue to investigate methods to accurately estimate lake trout mortality; Examine the influence of life stage and stocking practices on prevalence of natural reproduction, rather than just survival of stocked fish; Investigate the home range of stocked and wild lake trout with respect to needs for harvest management. 33

41 CONCLUSION Lake trout rehabilitation remains an important goal for Lake Huron management agencies. While progress has been slow in some areas, we have learned enough over the past decade (e.g. Johnson and VanAmberg 1995; Reid et al. 2001; Dobiez et al. 2005; Riley et al. 2007; Bence et al. 2008; Morbey et al. 2008) to be optimistic that rehabilitation is indeed achievable. In particular, recent wide spread increases in production of wild lake trout across much of the lake are cause for optimism for the program. In fact, in some rehabilitation zones the most recent review suggests that substantial progress has been made and that the short term objective may be close to achievement. However, concurrent widespread declines in abundance confound our understanding of progress and lend some uncertainty to decisions regarding stocking. If lake trout rehabilitation can be achieved, it is expected to represent the primary means to create stability in the Lake Huron fish community, along with prevention of further exotic species introductions. This revised Rehabilitation Plan and its primary Goal reflect a continued commitment from the OMNR to this end. This revised Plan builds on past efforts, namely Argyle et al. (1991), Ebener (1998) and most importantly, OMNR (1996). This Plan provides recommendations that reflect new understanding about rehabilitation discussed in the recent Review of the 1996 Plan and rehabilitation efforts in Ontario waters (OMNR 2009). The concept of a progression through rehabilitation is fundamental and provides the basis for revised Objectives and a decision making process that more realistically reflects the influence of stocking on the timing of rehabilitation (Figure 6). The primary actions identified in this Plan that will be implemented include: Continued identification of lake trout rehabilitation zones as areas within which to focus rehabilitation activities; Continued stocking in rehabilitation zones where signs of rehabilitation are lacking; Evaluation of paired plant and pulse stocking experiments in a rehabilitation context; Management of lake trout fishing mortality through fishery controls and conversions to live capture commercial gear types or gear types that minimize lake trout catches where possible; Implementation of standardized assessment protocols to collect data for evaluation of progress towards rehabilitation; Calculation of standard metrics by which to evaluate progress towards rehabilitation objectives; Continued advocacy for sea lamprey control and lake trout research. Important differences between this Plan and the 1996 Plan include: Revised Objectives that better consider the expected influence of stocking on the timing of rehabilitation in each LTRZ; 34

42 Revised LTRZ boundaries that reflect the influence of habitat on the distribution of lean lake trout; Addition of a deep water LTRZ to facilitate the introduction of deep water lake trout strains; Reduced spatial coverage for LTRZ 10 to focus efforts in areas where natural reproduction has been observed; Stocking target densities of 4.5 yearlings/hectare rather than 2.5 yearlings/hectare; Explicit recommendations to reduce fishing mortality through fishery regulation and incentives for the commercial fishery by conversion to live capture gear types (trap nets) or other gear types that minimize lake trout catches; More discreet, measurable evaluation criteria that allow for clearer evaluation of progress towards Objectives; Use of a limited suite of standardized assessment methods that gather data for calculation of evaluation criteria; Inclusion of LTRZ specific stocking, assessment and management activities (see Appendix A). Figure 6. Flowchart describing a management decision model and recommended actions as rehabilitation objectives are achieved. 35

43 In conclusion, the collapse of native lake trout populations in Lake Huron ushered in an era of uncertainty and instability in the fish community. Rehabilitation of wild lake trout populations is still considered achievable and the best way to reverse this situation and promote a balanced, stable ecosystem. Such an ecosystem will ultimately provide the most benefits at the lowest cost to society. 36

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51 Ryder, R.A., and Edwards, C.J. Eds A conceptual approach for the application of biological indicators of ecosystem quality in the Great Lakes basin. Int. Joint Comm. And Great lakes Fish. Comm., Windsor, ON. Selgeby, J.H., Bronte, C.R., Brown Jr., E.H., Hansen, M.J., Holey, M.E., VanAmberg, J.P., Muth, K.M., Makauskas, D.B., McKee, P., Anderson, D.M., Ferreri, C.P., and Schram, S.T Lake trout restoration in the Great Lakes: stock size criteria for natural reproduction. J. Great Lakes Res. 21(Suppl. 1): Sitar, S.P, Bence, J.R., Johnson, J.E., Ebener, M.P., and Taylor, W.W Lake trout mortality and abundance in southern Lake Huron. N. Am. J. Fish. Man. 19: Spangler, G.R., and Berst, A.H Performance of lake trout (Salvelinus namaycush) backcrosses, F 1 splake (S. fontinalis x S. namaycush), and lake trout in Lake Huron. J. Fish. Res. Bd. Can. 33: Stewart, T.J., Lange, R.E., Orsatti, S.D., Schneider, C.P., Mathers, A., and Daniels, M.E Fish-community objectives for Lake Ontario. Great Lakes Fish. Comm. Spec. Pub. 99-l. 56 p. Stott, W Natural Lake trout Strain Identification in Lake Huron. Research Completion Report for Fisheries Research Project #03E3MI , Great Lakes Fishery Commission. 44

52 A Revised Lake Trout Rehabilitation Plan for Ontario Waters of Lake Huron: Appendices A, B and C Upper Great Lakes Management Unit - Lake Huron

53 Upper Great Lakes Management Unit, Lake Huron Office A Revised Lake Trout Rehabilitation Plan for Ontario Waters of Lake Huron: Appendices A, B and C May 4, 2012 Ontario Ministry of Natural Resources Upper Great Lakes Management Unit, Lake Huron Office 46

54 TABLE OF CONTENTS LIST OF FIGURES...IV LIST OF TABLES...VI APPENDIX A: LAKE TROUT REHABILITATION ZONE PLANS... 1 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...2 Stocking...3 Assessment...3 Management...3 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...4 Stocking...5 Assessment...5 Management...5 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...6 Stocking...7 Assessment...7 Management...7 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...8 Stocking...9 Assessment...9 Management...9 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...10 Stocking...11 Assessment...11 Management...11 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...12 Stocking...12 Assessment...13 Management...13 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...14 Stocking...15 Assessment...15 Management...15 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...16 Stocking...17 i

55 Assessment...17 Management...17 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...18 Stocking...19 Assessment...19 Management...19 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...20 Stocking...21 Assessment...21 Management...21 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...22 Stocking...23 Assessment...23 Management...23 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...24 Stocking...25 Assessment...25 Management...25 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...26 Stocking...27 Assessment...27 Management...27 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date Stocking Assessment...29 Management...29 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...30 Stocking...31 Assessment...31 Management...31 LAKE TROUT REHABILITATION ZONE Overview and Progress to Date...32 Stocking...33 Assessment...33 Management...33 LAKE TROUT REHABILITATION ZONE Stocking...34 Assessment...35 Management...35 ii

56 APPENDIX B: DESCRIPTION OF LAKE TROUT ASSESSMENT PROTOCOLS APPENDIX C: SCORING MATRIX USED TO RANK LTRZS IN ONTARIO WATERS OF LAKE HURON iii

57 LIST OF FIGURES Figure 1. The revised boundaries of LTRZ 1, lake trout spawning shoals, the 40 fathom contour, future stocking sites and the Drummond Island Refuge....2 Figure 2. The revised boundaries of LTRZ 2, lake trout spawning shoals, as well as existing and proposed stocking sites...4 Figure 3. The revised boundaries of LTRZ 3, lake trout spawning shoals, and existing stocking sites...6 Figure 4. The revised boundaries of LTRZ 4, lake trout spawning shoals, the 40 fathom contour and existing stocking sites...8 Figure 5. The revised boundaries of LTRZ 5 and existing stocking sites...10 Figure 6. The revised boundaries of LTRZ 6 and the 40 fathom contour...12 Figure 7. The revised boundaries of LTRZ 7, lake trout spawning shoals, the 40 fathom contour and existing stocking sites...14 Figure 8. The revised boundaries of LTRZ 8, lake trout spawning shoals, the 40 fathom contour and existing stocking sites...16 Figure 9. The revised boundaries of LTRZ 9, lake trout spawning shoals, the 40 fathom contour and existing stocking sites...18 Figure 10. The revised boundaries of LTRZ 10, lake trout spawning shoals, the 40 fathom contour and existing stocking sites...20 Figure 11. The revised boundaries of LTRZ 11, lake trout spawning shoals, the 40 fathom contour and existing stocking sites...22 Figure 12. The revised boundaries of LTRZ 12, lake trout spawning shoals and the 40 fathom contour...24 Figure 13. The revised boundaries of LTRZ 13, lake trout spawning shoals, the 40 fathom contour as well as existing and proposed stocking sites Figure 14. The revised boundaries of LTRZ 14, lake trout spawning shoals, the 40 fathom contour and proposed stocking sites...28 Figure 15. The revised boundaries of LTRZ Figure 16. The revised boundaries of LTRZ iv

58 Figure 17. The boundaries of LTRZ 17, a new rehabilitation zone v

59 LIST OF TABLES Table 1. Proposed Lake Huron (Ontario waters) lake trout stocking activities for the period LTRZ 6 is rehabilitated and will not be stocked. LTRZs 3, 15 and 11 have recently reached the mid-term objective and will not be stocked. LTRZs 2, 5, 7, 8, 9 and 14 are those where stocking will be conducted while zones 4, 10 and 13 will not be stocked given the limited availability of fish from Provincial hatcheries. LTRZs 1, 12 and will not be stocked as these are in-active zones. Bolded rows indicate new or proposed stocking sites Table 2. Proposed Lake Huron (Ontario waters) lake trout fishery independent assessment activities for the period (see acronym definitions in Appendix B). Shaded columns indicate past years and bolded entries indicate proposed assessment projects that were not conducted. Projects that were planned but not conducted have been carried forward. LTRZ 6 is rehabilitated and will not be stocked; assessment will continue to assess status in this zone. LTRZs 3, 11 and 15 have recently reached the mid term objective and will not be stocked as a result; the indicated assessment projects will determine the status of lake trout in these zones in the absence of stocking. Zones with priority ranks 2-3, 6, and 14 are those where stocking will actually be conducted given the availability of fish from Provincial hatcheries. Note that although no lake trout specific surveys are planned in zones with ranks 7-8, and 15-17, lake trout data will be collected in these zones through commercial catch sampling efforts, offshore index surveys or by the USFWS in the case of LTRZ vi

60 APPENDIX A: LAKE TROUT REHABILITATION ZONE PLANS In the Review of lake trout rehabilitation in Ontario waters, it became clear that specific direction was required for stocking, assessment and management actions within each Lake Trout Rehabilitation Zone (LTRZ) (OMNR 2009). Stocking of pure-strain lake trout started at different times in most LTRZs and stressors such as exploitation and sea lamprey induced mortality often varied between LTRZs (OMNR 2009). Given these differences, attainment of each rehabilitation objective was/is expected to occur at different times in each LTRZ. It is also expected that stocking, assessment and management activities will be different in most of the 17 LTRZs in any given year. In order to provide clear, explicit directions, detailed summaries are provided for each LTRZ. These will provide a brief overview of each LTRZ along with a synopsis of progress towards rehabilitation to date. The summaries will also include the following including: 1) which, if any, rehabilitation objectives have been achieved; 2) a description of stocking (including number of fish to be stocked, strain, age, location etc); 3) assessment activities to be conducted; and 4) management actions to be implemented. The proposed stocking, assessment and management actions for each LTRZ will depend on the status of rehabilitation and objectives achieved to date. Following these summaries for each LTRZ, an approach for coordinated yearly stocking and assessment activities across all LTRZs will be included to provide a lakewide perspective, through the inclusion of two tables at the end of this Appendix. It is expected that stocking and assessment activities will be constrained by limits on the available resources and as a result, this document will need to be re-visited on a yearly basis and revised accordingly, namely these tables. It should be noted that these two tables reflect the combined impacts of the ranking process, progress towards rehabilitation in each zone and production capacity from MNR hatcheries on where fish will be stocked and what assessment work the UGLMU will conduct. 1

61 LAKE TROUT REHABILITATION ZONE 1 Lake Trout Rehabilitation Zone 1 is located in the western end of the North Channel (Figure 1). It encompasses all the Canadian waters from the eastern shore of St. Joseph Island, eastward to a line running between the western end of Manitoulin Island and the western side of Mississagi Bay. This LTRZ lies in close proximity to the Drummond Island Refuge, a priority lake trout rehabilitation zone in American waters. Figure 1. The revised boundaries of LTRZ 1, lake trout spawning shoals, depths greater than 40 fathoms, future stocking sites and the Drummond Island Refuge. Commercial fisheries in this area target walleye (Sander vitreus) close to St. Joseph s Island and some lake whitefish (Coregonus clupeaformis). Recreational fisheries target Chinook salmon (Oncorhynchus tshawytscha) in the offshore waters as well as walleye and cisco (Coregonis artedii) closer to St. Joseph Island and the St. Mary s River. Overview and Progress to Date Only two stocking events have occurred in this zone (due to a hatchery emergency) as stocking has been deferred due to high sea lamprey abundance. As a result, lake trout that have been sampled in this zone are immigrants, largely from American stocking activities in the nearby 2

62 Drummond Island refuge and LTRZ 2. Sea lamprey wounding rates have and continue to be very high in this zone as observed in both of the recent reviews. With this in mind, sea lamprey induced mortality needs to be evaluated into the future to determine if it continues to be a major impediment to lake trout rehabilitation and if stocking is reasonable at some point in the future. Although sea lamprey wounding rates are high in this zone, the proportion of wild fish caught in the commercial fishery has increased noticeably since 2006 while the mean age of lake trout sampled in the commercial fishery has also been above the mean age to maturity in recent years. However, very low CUEs and high sea lamprey wounding rates would suggest that this zone has not achieved the short term rehabilitation objective. Stocking Although sea lamprey abundance continues to be high in this zone, it is hoped that sea lamprey control efforts in the St. Mary s River are reducing lamprey abundance in the North Channel to more reasonable levels. Once wounding falls below an average of 10 wounds/100 fish over a three-year period, stocking at the new target density of 4.5 yearlings/ha (499,689 fish), may be implemented. Stocking will be conducted by boat or barge to allow fish to be stocked in close proximity to known spawning habitat. In order to place the stocked fish in multiple locations, two stocking locations have been identified for this LTRZ (Figure 1). Assessment Commercial catch sampling will be a priority and will target 200 lake trout biological samples and 50 coded-wire-tagged fish (CWT) per year in this LTRZ. This includes a concerted effort to gather sea lamprey wounding data from sampled lake trout given the high wounding rates observed in this LTRZ in the past. If stocking is implemented in this zone, offshore index assessment surveys should be implemented for two years consecutively, starting four years after stocking commences (when the first cohort of stocked fish are five years of age). Pending no major problems or impediments, spawning surveys using large-mesh gillnet gear should be implemented starting seven years after stocking commences (when the first cohort of stocked fish are eight years of age), for a two-year period, to verify the presence of a spawning population. Management Continued concerted lamprey control in the St. Mary s River and North Channel tributaries is required for rehabilitation to occur in this LTRZ. The use of live capture gear (trap nets) should be encouraged in the commercial fishery by exploring the concept of enhancing whitefish quotas and the use of economic incentives such as preferential royalty rates for fisheries using this gear. Alternatively, restrictive management actions may be required to ensure lake trout annual mortality rates are kept below 40%. 3

63 LAKE TROUT REHABILITATION ZONE 2 Lake Trout Rehabilitation Zone 2 is located in the eastern end of the North Channel, and extends from Barrie Island east to Little Current. It includes all of the waters from the north shore of the North Channel to Manitoulin Island (Figure 2). While waters deeper than 35m are limited, there is extensive shoreline and shoal spawning habitat. Figure 2. The revised boundaries of LTRZ 2, lake trout spawning shoals, as well as existing and proposed stocking sites. Overview and Progress to Date The commercial fishery in LTRZ 2 targets lake whitefish, as well as walleye and yellow perch (Perca flavescens). In recent years, gillnets have been used exclusively by commercial fishers in this LTRZ; however, some live capture gear has historically been used in this zone. Commercial fishing activity is excluded from the eastern third of the zone. Recreational fisheries focus on near shore species such as walleye and northern pike (Esox lucius), although in recent years, fisheries for Chinook salmon, rainbow trout (Oncorhynchus mykiss), and lake trout have developed. Stocking rates in this LTRZ have generally been below the old target density of 2.5 yearlings/ha. A paired plant experiment using Parry Sound and Iroquois Bay strains has been 4

64 occurring in this zone since These fish have been shore stocked in Gore Bay (Figure 2). There is evidence of only a modest lake trout population in this LTRZ. Sea lamprey wounding rates have been consistently high and in recent years have been 4-5 times the target of 5 wounds per 100 lake trout. The age distribution of lake trout caught in the commercial fishery in this zone has expanded since 2006 and total annual mortality rates have been below the target of 40%. However, very low catch rates and low proportions of wild fish in catches, plus the extremely high sea lamprey wounding rates indicate that LTRZ 2 has not yet achieved the shortterm rehabilitation objective. Stocking The stocking component of a paired experiment currently underway in this zone should be terminated. Pending the results of the paired plant experiment, Iroquois Bay strain lake trout should be stocked in this LTRZ as the source for this native strain is in close proximity to this LTRZ. These fish should be stocked at the new target density of 4.5 yearlings/ha (520,938 fish). Fish should be stocked in at least two locations in the zone; boat stocking in close proximity to the known spawning habitat in this LTRZ is the preferred option (Figure 2). However, due to limited boat stocking capability, shore stocking a portion of the fish in this zone is likely to continue at the current location in Gore Bay (Figure 2). Stocking a larger proportion of the fish in the eastern end of the zone is likely the most effective strategy given the absence of a commercial fishery in this portion of the LTRZ. At a minimum, the allocation of stocked fish should be evenly split between the eastern and western halves of the LTRZ. Assessment Commercial catch sampling will be a priority and will target 200 lake trout biological samples and 50 CWT recoveries per year in this LTRZ. This includes a concerted effort to gather sea lamprey wounding data from sampled lake trout given the high wounding rates observed in this LTRZ in the past. Although stocking rates have been below the old target density and sea lamprey abundance continues to be high, targeted spawning assessments using large-mesh gillnet gear in support of the paired plant experiment should be implemented by 2010, for a two year period, in an effort to detect whether a spawning population exists in this LTRZ and to recover CWTs. Management Continued emphasis on the need for concerted lamprey control in the St. Mary s River and North Channel tributaries is required for this LTRZ. The use of live capture gear (trap nets) should be encouraged in the commercial fishery by exploring the concept of enhancing whitefish quotas and the use of economic incentives such as preferential royalty rates for fisheries using this gear. Alternatively, restrictive management actions may be required to ensure lake trout annual mortality rates are kept below 40%. 5

65 LAKE TROUT REHABILITATION ZONE 3 Lake Trout Rehabilitation Zone 3 is located in the northwest corner of Georgian Bay. It begins at Little Current in the west and includes Manitowaning Bay, Frazer Bay and the waters of Georgian Bay between Cape Smith and Killarney (Figure 3). The area contains several historic lake trout spawning shoals, along with numerous islands and extensive shoreline spawning habitat. Although deeper water is limited within this LTRZ, deepwater habitat is available to the east in Georgian Bay. Figure 3. The revised boundaries of LTRZ 3, lake trout spawning shoals, and existing stocking sites. Overview and Progress to Date A relatively small commercial fishery currently operates in this zone targeting lake whitefish, round whitefish (Coregonus cylindraceum), as well as some yellow perch and walleye. Recreational fisheries target lake trout, smallmouth bass (Micropterus dolomieu), and northern pike, with winter fisheries targeting lake trout and lake herring. Stocking has been at or above the old target stocking density since 1995 and has been comprised of Iroquois Bay strain fish since Relative abundance of lake trout has been increasing in this zone for several years and appears to be higher than many other LTRZs although CUE 6

66 remains below target levels. The average age of lake trout in this zone is now at or above the target of 7 years of age (the mean age to maturity) and multiple cohorts of mature lake trout have been observed on spawning habitat. Total annual mortality rates are low but sea lamprey wounding rates have recently increased above the target level. Wild fish dominated catches in fall 2009 and 2010 assessment projects. All targets have been met in this LTRZ except abundance and sea lamprey marking targets. This lends some uncertainty to decisions regarding stocking but it appears that this zone may have attained the mid-term rehabilitation objective in recent years. Stocking With wild fish dominating catches in recent surveys, continued stocking in LTRZ 3 comes into question as it appears that the mid-term objective has been reached. Recent advice from the scientific community would suggest that cessation of stocking in this zone is a reasonable course of action. As a result, stocking will be terminated in this LTRZ. Assessment Commercial catch sampling will be a priority and will target 200 lake trout biological samples and 50 CWT recoveries per year in this LTRZ. As pure strain lake trout stocking commenced in 1992 and has exceeded the old target stocking density of 2.5 yearlings/ha since 1996, population surveys using the FLIN protocol were conducted in 2009 and 2010 (this protocol was last used in 2004 in this zone) to verify the presence of a spawning stock and determine whether wild fish were present. These surveys should be conducted on a five-year rotational basis to track changes in this population and to ensure that progress towards the long-term objective occurs in the absence of stocking. Additionally, creel surveys should be contemplated given anecdotal accounts of a growing recreational fishery for lake trout in this zone. Management Monitor commercial fishing activity in this zone through on-board sampling, however, the commercial fishery does not appear to be an impediment to rehabilitation in this LTRZ at this time. Discuss with stakeholders the need for recreational fishing regulation changes to ensure survival of wild fish in this LTRZ. 7

67 LAKE TROUT REHABILITATION ZONE 4 The Grand Bank/Dawson Rock LTRZ is located in northern Georgian Bay and is currently the only legislated fish sanctuary in Canadian waters of Lake Huron protecting lake trout spawning habitat. This LTRZ encompasses spawning shoals, numerous reefs and small islands surrounded by extensive deepwater habitat. The sanctuary itself is 36,060 ha and encompasses the shaded area indicated in Figure 4. Figure 4. The revised boundaries of LTRZ 4, lake trout spawning shoals, depths greater than 40 fathoms and existing stocking sites. Overview and Progress to Date While no fishing is allowed within the sanctuary, small commercial fisheries do exist in the surrounding waters. These target mainly lake whitefish and deepwater chub (Coregonus hoyi). There is minimal recreational fishing in the area surrounding this sanctuary given the distance from suitable harbours. Fish intended for stocking in this zone have often been stocked before reaching the zone due to the distance from a suitable port and the influence of poor weather. The distance from ports to this LTRZ has also hampered assessment efforts; as a result only one assessment survey has been conducted in this zone in recent years. Lake trout catches were low in this survey, no wild 8

68 fish were observed and sea lamprey wounding rates were well above target levels. The shortterm objective has not been achieved in this LTRZ. Stocking Stocking should continue on a yearly basis using Michipicoten strain at the new target density of 4.5 yearlings/ha (162,270 fish) (Figure 4). However, this zone does rank low in the priority ranking list for the LTRZs and as a result there may not be enough capacity from Provincial hatcheries to continue to stock fish. If and when stocking does occur, priority should be given to ensure that fish are stocked within the zone, in close proximity to spawning habitat. This may require the use of larger stocking vessels than are currently in use by the Upper Great Lakes Management Unit (UGLMU). Additionally, increased flexibility in stocking may be required to accommodate the logistical challenges this zone presents (i.e. distance from port and the impacts of poor weather). Assessment Due to the sanctuary status of this zone, data from fishery-dependant sources are not available. Additionally, the exposed nature of this zone makes fall spawning surveys difficult due to inclement fall weather. Stocking of pure strain lake trout commenced in 1988 albeit at inconsistent and often low levels and a fisheries-independent survey conducted in 2006 indicated that stocking has been largely ineffective to that time. As a result, any independent assessments should not be conducted until stocking levels have stabilized at or near target densities, and fish have been stocked in close proximity to spawning habitat within the LTRZ. If these two conditions are met consistently, offshore index assessment surveys should be implemented for two years consecutively, starting four years after stocking commences (when the first cohort of stocked fish are five years of age). Pending no major problems or impediments, spawning surveys using large mesh gillnet gear should be implemented starting seven years after stocking commences (when the first cohort of stocked fish are eight years of age), for a two-year period, to verify the presence of a spawning population. Management The sanctuary status of this zone should be maintained. 9

69 LAKE TROUT REHABILITATION ZONE 5 Lake Trout Rehabilitation Zone 5, Iroquois Bay, is one of two LTRZs in Lake Huron with a remnant lake trout stock. It is located in the extreme northwest corner of Georgian Bay and is relatively isolated from the contiguous waters of the North Channel and northern Georgian Bay (Figure 5). This secluded bay is characterized by several near-shore spawning shoals and deep offshore habitat. The total area of LTRZ is only 496 ha. Figure 5. The revised boundaries of LTRZ 5, lake trout spawning shoals and existing stocking sites. Overview and Progress to Date No commercial fishery exists in Iroquois Bay, although First Nation subsistence fishing has occurred sporadically in the past. Iroquois Bay supports recreational fisheries during openwater and winter periods, traditionally targeting lake trout, muskellunge (Esox masquinongy), and smallmouth bass. This LTRZ has been stocked at densities higher than any other LTRZ. Fisheries-independent surveys suggest that survival of stocked fish is high, however an adult population comprised of either stocked or wild fish, does not appear to be building. Spawning surveys conducted in the 1990s, and in 2004 indicated that only small numbers of large, old fish were present in the 10

70 spawning population, FLIN surveys conducted at the same time as spawning surveys indicated that wild juveniles were being produced up until the mid-2000s. FLIN surveys conducted in 2009 and 2010 did not catch any wild lake trout of any age group however. Past creels indicated relatively high yields of lake trout in recreational fisheries; this may have imposed excessive mortality on adult and sub-adult lake trout. Strict recreational fishing regulations were implemented in In the absence of more recent creel data, anecdotal information suggests that angling effort targeting lake trout has declined to a large degree. While the shortterm objective may not strictly apply given the presence of a remnant stock in this zone, the recovery of the lake trout population in the zone appears to be inhibited. Stocking Stocking rates should be reduced to a target density of 2.25 yearlings/ha (2,313 fish) half of the new target density of 4.5 yearlings/ha. This reduced stocking density recognizes that natural reproduction has been observed in this LTRZ. Additionally, stocking should be conducted on an alternate year basis to both help minimize competition with the few wild juveniles that are produced, while still providing stocked fish to bolster faltering natural reproduction. Current shore stocking locations are suitable for future use given the small size of Iroquois Bay (Figure 5). Only Iroquois Bay strain fish should be stocked in this zone. Assessment Progress towards rehabilitation appears to be impeded in this zone. As a result, assessment netting should remain focused on characterizing the existing lake trout population in this zone, in particular spawning-aged fish. Given the presence of a remnant population, short-set FLIN gillnetting on or near spawning grounds was conducted in 2009 and 2010 to monitor the rates of natural reproduction in the juvenile component of the population and characterize the entire population. This should be conducted on a five-year cycle. Although trap nets were used for similar assessment needs in Parry Sound, steep shoreline habitats in Iroquois Bay are not conducive to the use of trap nets. Tagging should also be conducted during gillnetting operations to allow the calculation of mark-and-recapture population estimates. Management Iroquois Bay is only one of two locations in Lake Huron with a remnant stock. The importance of sustaining and improving the status of this population cannot be overstated. Harvest of lake trout in this zone is confined to a highly regulated recreational fishery. As the only source of harvest, the recreational fishery appears to be the only remaining source of mortality over which fisheries managers have control. As a result, the only remaining regulatory option available in this zone is complete closure of the lake trout fishery. Recent studies (fall 2009 and 2010; OMNR unpublished data) which captured few to no wild fish indicate that this last remaining management option should be implemented as soon as possible until such time as natural reproduction is significant and sustainable, and population metrics meet criteria set out in this plan. 11

71 LAKE TROUT REHABILITATION ZONE 6 Lake Trout Rehabilitation Zone 6 is located in eastern Georgian Bay. It includes Parry Sound and the waters out to the western point of Parry Island, and includes waters captured within Killbear Provincial Park (Figure 6). It is characterized by numerous spawning shoals and adjacent deepwater habitat. Like Iroquois Bay, Parry Sound supports one of only two remnant Great Lakes lake trout populations outside of Lake Superior. Figure 6. The revised boundaries of LTRZ 6, lake trout spawning shoals and depths greater than 40 fathoms. Overview and Progress to Date Lake trout rehabilitation in this LTRZ has occurred with the long-term objective met, as documented in Reid et al. (2001). This LTRZ supports a very highly regulated recreational fishery. Fishery controls continue to be relatively restrictive to protect and enhance the rehabilitated lake trout population. Evidence of movement into the surrounding waters of Georgian Bay suggests that lake trout from Parry Sound are expanding their range. Stocking 12

72 Stocking was terminated in Parry Sound in 1997 in response to evidence that the lake trout population in this zone was recovering. Stocking in the adjacent Five Mile Bay has continued annually since Five Mile Bay represents marginal lake trout habitat given its shallow depth and as such, is not a suitable location to continue stocking lake trout. However, its historic use by lake trout suggests that wild lake trout from Parry Sound proper may ultimately utilize Five Mile Bay for some part of their life cycle. Assessment Trap netting on the spawning grounds, FLIN surveys, and creel surveys should be conducted every five years, for two consecutive years, to monitor the status of the lake trout population and the impacts of the fishery in this LTRZ. Conducting this suite of assessment projects will emulate those that have been conducted in the past in Parry Sound. The next cycle of assessment should start in Management Current recreational and commercial fishing regulations in place in this LTRZ should be maintained. 13

73 LAKE TROUT REHABILITATION ZONE 7 Lake Trout Rehabilitation Zone 7 is located in eastern Georgian Bay and encompasses the Limestone Islands to the northwest of Parry Sound (Figure 7). The area is comprised of several islands, reefs and shoals and includes abundant spawning, nursery and summer habitat for lake trout. Figure 7. The revised boundaries of LTRZ 7, lake trout spawning shoals, depths greater than 40 fathoms and existing stocking sites. Overview and Progress to Date This LTRZ has been part of a pulse-stocking experiment (which involves three years stocked followed by three years without stocking) since 1997 and has been stocked at higher than normal densities, although many of the fish were not stocked within the zone boundaries or in close proximity to spawning habitat. A small commercial fishery that operated in portions of this LTRZ was retired in This LTRZ was to be given sanctuary status but the sanctuary was never formally established. A spring 2006 fishery independent survey captured few fish however, mortality rates were low and large, old fish were present. A fisheries independent survey conducted in 2008 indicated that the mean age was above the target, total annual mortality was below the upper threshold of 40% and that wild lake trout represented over 50% of the catch. However, target CUEs were not reached in this survey as has been the case in 14

74 other LTRZs recently. Despite this caveat, it appears that this LTRZ may be approaching attainment of the short term objective. Uncertainty does exist with respect to continued stocking given low catch rates in assessment surveys. Stocking Pulse stocking should be continued for three full cycles at densities similar to recent stocking events. As a result, 400,000 Parry Sound strain fish were stocked at a density of 5.59 yearlings/ha from 2009 to 2011, the final of three pulses of stocking in this zone. A decision regarding continued stocking will need to be made by 2013 to ensure that Provincial hatcheries can provide fish for future stocking in this zone. At this time, continued stocking is foreseeable given the low catch rates in this LTRZ despite mounting numbers of wild fish. Assessment Recent catches of unclipped fish in this zone suggest that the short-term objective has likely been achieved in this LTRZ and that spawning surveys are not required. Additionally, the distance from nearby ports and the exposed nature of this LTRZ largely prevent the implementation of fall spawning surveys during often inclement fall weather. As a result, offshore index assessment surveys should be implemented over a two-year period staring in 2011 to track changes in the lake trout population in this LTRZ, to determine if the mid-term objective is achieved and to help educate future decisions regarding the need for continued stocking. These surveys should be repeated over a five-year cycle. Management Sanctuary status should be implemented for this zone. 15

75 LAKE TROUT REHABILITATION ZONE 8 Lake Trout Rehabilitation Zone 8 is located in the southeast corner of Georgian Bay and is focused on the Watcher Island complex (Figure 8). The Watcher Island complex (the Watchers) is characterized by an abundance of lake trout spawning habitat with nearby deepwater habitat. Figure 8. The revised boundaries of LTRZ 8, lake trout spawning shoals, depths greater than 40 fathoms and existing stocking sites. Overview and Progress to Date A commercial fishery exists in the area, targeting primarily lake whitefish, with some harvest of deepwater chub, walleye, and yellow perch. Recently, lake trout have become a large component of the commercial harvest. Recreational fisheries in the area focus on near-shore species such as walleye, northern pike, and smallmouth bass. Fisheries for lake trout and Chinook salmon have also developed in offshore regions of this LTRZ. This LTRZ has been part of a pulse-stocking experiment (which involves three years stocked followed by three years without stocking) since 2000 and has been stocked at higher than normal densities. However, many of the fish were not stocked in close proximity to spawning habitat at the Watcher Islands or, in some cases, within the zone boundaries. Reporting from the 16

76 commercial fishery did demonstrate that abundance of lake trout increased dramatically following the first pulse stocking events however, numbers of lake trout from subsequent pulse stocking events recruiting to the commercial fishery appear to be substantially lower. Estimated lake trout mortality rates have been very high in this LTRZ, particularly for fish from the first pulse stocking events, and fishing mortality will continue to be a key factor in determining how many of the stocked lake trout survive to maturity in this LTRZ. Lamprey wounding rates have been above target levels since 2004 and few wild fish have been observed in this LTRZ. It is clear that this LTRZ has not yet achieved the short-term rehabilitation objective. Stocking Pulse stocking should be continued for three full cycles at densities similar to recent stocking events. This will entail stocking 400,000 Parry Sound strain fish at a density of 8.65 yearlings/ha from 2012 to It is very important that the fish be stocked in close proximity to spawning habitat within the zone (Figure 8). Assessment Commercial catch sampling should be enhanced to ensure 200 lake trout samples are collected annually in this LTRZ. Additionally, standard offshore index assessment netting was conducted in 2009 and 2010 to characterize the lake trout population in this LTRZ given its stocking history. Results from these surveys continued to indicate a lack of progress towards rehabilitation in this zone. If progress is to be made, mortality rates will need to be reduced. If this occurs, further OSIA projects should be conducted 4 years after mortality rates are reduced. Continued yearly sampling of the commercial catch will be crucial to evaluating the status of lake trout in this LTRZ in the interim. Management High mortality rates in this LTRZ, associated with commercial fishing, have likely contributed to the failure in achieving the short-term objective. Due to these high mortality rates, the use of live-capture gear (trap nets), or gill-nets modified to reduce incidental catches of lake trout, should be encouraged in the commercial fishery. This could be facilitated by exploring the concept of incentives when using these alternative gear types to reduce mortality rates. A large proportion of the commercial fishery in this LTRZ has been inactive in recent years. If commercial fishing activity increases, restrictive management actions may be required to ensure lake trout annual mortality rates are kept below 40%. 17

77 LAKE TROUT REHABILITATION ZONE 9 Lake Trout Rehabilitation Zone 9 encompasses all of Nottawasaga Bay from Christian Island in the east to Cape Rich in the west (Figure 9). The area contains several near-shore spawning shoals, including the Mary Ward Ledges, a large series of reefs and shoals. Deepwater habitat is found in the central and western areas of the zone. Figure 9. The revised boundaries of LTRZ 9, lake trout spawning shoals, depths greater than 40 fathoms and existing stocking sites. Overview and Progress to Date The largest commercial fishery in Georgian Bay is found within Nottawasaga Bay which is captured in its entirety by LTRZ 9. Commercial fishing activity traditionally targets lake whitefish and deepwater chub. Recreational fisheries target non-native salmonids and lake trout, as well as smallmouth bass in near-shore areas. Stocking of pure-strain lake trout started in 1993 and a paired plant experiment using Parry Sound and Seneca strains started in 1999 in this zone. Stocking rates have been above the target rate for most years when pure-strain lake trout were stocked. Short-term survival of stocked fish was high during the 1990s and the mean age of captured lake trout has slightly surpassed the target in recent years. The proportion of wild fish increased from near zero to over 40% by 18

78 2008 but has declined since. From 1996 to 2004 catch rates in a fisheries independent survey in this zone were at or above the target of 8 fish per net but have declined to near zero since. Total annual mortality rates have often been high in this zone but declined to just below threshold levels from Sea lamprey wounding rates have often been below the threshold of 5 wounds per 100 lake trout but in 2009 and 2010, increased to levels nearly double the threshold value. LTRZ 9 has yet to attain the short-term objective of establishing a sufficiently large spawning stock. Stocking The stocking component of the paired experiment currently underway in this zone should be terminated. Pending the results of the paired plant experiment, Parry Sound strain should be stocked as it is a native strain whose source is located in relatively close proximity to this LTRZ. Parry Sound strain fish should be stocked at the new target density of 4.5 yearlings/ha (563,125 fish) at the Mary Ward Ledges (Figure 9). This will ensure that fish are stocked in close proximity to spawning habitat and also to allow separation from fish stocked in LTRZ 10. Assessment Commercial catch sampling will be a priority and will target 200 lake trout biological samples and 50 CWT recoveries per year in this LTRZ. Additionally, offshore index assessment netting which has been conducted since 1978 in this LTRZ should continue to be conducted on an annual basis. Pending the outcome of index surveys and in conjunction with data collected during on-board catch sampling, spawning surveys using large-mesh gillnet should be implemented in 2013 and 2014 to determine if a spawning population exists in this LTRZ. Management Recent declines in overall abundance of lake trout and numbers of wild fish suggest that survival is an issue for lake trout in this zone. Consequently, the use of live-capture gear (trap nets), or gill-nets modified to reduce incidental catches of lake trout, should be encouraged in the commercial fishery. This could be facilitated by exploring the concept of incentives when using these alternative gear types to reduce mortality rates. Bottom substrates and bathymetry appear to be similar to the areas of the main basin where commercial trap nets are fished effectively suggesting that trap nets may be a viable option for the commercial fishery in this zone. Alternatively, restrictive management actions may be required to ensure lake trout annual mortality rates are kept below 40%. 19

79 LAKE TROUT REHABILITATION ZONE 10 Lake Trout Rehabilitation Zone 10 is located in southwestern Georgian Bay (Figure 10). This zone contains several historical lake trout spawning locations, most of which are near shore, although offshore reefs and islands also provide spawning habitat. This zone has abundant deepwater habitat. Figure 10. The revised boundaries of LTRZ 10, lake trout spawning shoals, depths greater than 40 fathoms and existing stocking sites. Overview and Progress to Date A commercial fishery exists in this LTRZ, which primarily targets lake whitefish and lake trout. Commercial activity has increased dramatically in recent years, although fishing normally occurs outside of Owen Sound and Colpoys Bays. A large recreational salmonid fishery exists within this LTRZ, primarily targeting non-native salmonids, although lake trout are also harvested. A fairly active winter recreational fishery for lake whitefish and lake trout exists when conditions permit. Stocking of pure-strain lake trout in this zone started in 1992 and since 2000 stocking densities have met the old target density of 2.5 yearlings/ha. Past assessment surveys indicated that overall numbers of lake trout and proportions of wild lake trout fluctuated at levels near targets 20

80 in this zone. However, recent fisheries independent surveys suggest that progress towards rehabilitation has stalled and both of these indicators have actually regressed. While total annual mortality rates are below the threshold in recent years, mean ages are below the mean age to maturity. Sea lamprey wounding rates have fluctuated above the target level in the past and increased dramatically in 2010 to five times the target level of 5 wounds per 100 lake trout. Although positive signs of progress were evident in this LTRZ in the 2006 review (OMNR 2009), it appears that past progress has stalled and that the short term objective has not been achieved. Stocking The ranking process that followed the most recent review placed this zone low in the list given the decline in the overall status of rehabilitation in this zone. As a result it is unlikely that this zone will b stocked. Should fish be available for this zone, stocking should be conducted using Parry Sound strain fish at the new target density of 4.5 yearlings/ha (319,680 fish) at the Big Bay Dock which is in close proximity to spawning habitat (Figure 10). The Parry Sound strain should be used as it is a native strain to Lake Huron. Assessment An evening spawning survey using short-set gillnets was conducted in 2009 and a FLIN survey was conducted in 2010 in this zone to both determine if the short-term objective had been achieved and to avoid mortality of wild fish that had been previously observed in spawning surveys. Logistical issues due to the exposed nature of this LTRZ were a problem in implementation of the evening survey in 2009, hence the move to the use of the daytime FLIN protocol in FLIN surveys should continue to be implemented on a three-year rotational basis, for two years consecutively, until the short term objective is achieved. Within LTRZ 10, these surveys should focus on spawning habitat located in close proximity to stocking locations. This includes spawning habitat surrounding White Cloud, Griffith, and Hay Islands and the shoreline around Big Bay (Figure 10). These surveys should include a mark-and-recapture component to estimate the size of the spawning population and movement of spawning-aged fish in this LTRZ. Continued implementation of this type of survey should be contemplated in 2017 and 2018 to assess whether the short-term objective has been achieved. Management Rehabilitation has stalled in this zone and it is likely that the short-term objective has not been achieved. As a result, the use of live-capture gear (trap nets), or gill-nets modified to reduce incidental catches of lake trout, should be encouraged in the commercial fishery. This could be facilitated by exploring the concept of incentives when using these alternative gear types to reduce mortality rates. Bottom substrates and bathymetry may be similar to the areas of the main basin where commercial trap nets are fished effectively suggesting that trap nets may be a viable option in this zone. Alternatively, restrictive management actions may be required to ensure lake trout annual mortality rates are kept below 40%. 21

81 LAKE TROUT REHABILITATION ZONE 11 Lake Trout Rehabilitation Zone 11 is located in the south-central region of the main basin of Lake Huron and is centered on Point Clark (Figure 11). Point Clark is the eastern extent of an underwater geological ridge called the Six Fathom Scarp that stretches across Lake Huron from Thunder Bay, Michigan. The area off of Point Clark has two large offshore reefs that have been identified as historical lake trout spawning sites. Although data are scarce, Point Clark was generally considered the most southerly lake trout spawning location in Ontario waters of the main basin. Deepwater habitat is readily available. Figure 11. The revised boundaries of LTRZ 11, lake trout spawning shoals, depths greater than 40 fathoms and existing stocking sites. Overview and Progress to Date A large commercial fishery exists immediately to the south of Point Clark. This fishery has expanded since 1994 in response to increased lake whitefish abundance in southern Lake Huron. A recreational fishery also operates in this LTRZ, targeting non-native salmonids and more recently lake trout. Some nearshore fishing also targets smallmouth bass and yellow perch. Pure-strain lake trout stocking started in 1993 in this LTRZ, and has generally been below target densities; immigration of stocked lake trout into this LTRZ from American waters is substantial. 22

82 The age distribution of lake trout in this LTRZ has shifted towards an older, more mature population with mean age increasing to near or above the mean age to maturity. Up to 2006 there was little evidence for natural reproduction but numbers of wild fish observed in the commercial fishery, derbies and fisheries independent surveys have increased substantially since Total annual mortality rates have generally below the threshold while sea lamprey wounding rates have been variable but above the target wounding rate of 5 wounds per 100 lake trout. Mean catch rates in fisheries independent surveys have not met targets. Increases in mean ages and wild fish abundance in this LTRZ indicate progress towards the mid-term objective although abundance targets have not been met as in some other LTRZs. This lends some uncertainty to decisions regarding stocking but it appears that this zone may have attained the mid-term rehabilitation objective. Stocking With wild fish dominating catches in recent surveys, continued stocking in LTRZ 3 comes into question as it appears that the mid-term objective has been reached. Recent advice from the scientific community would suggest that cessation of stocking in this zone is a reasonable course of action even though abundances may not be as high as is desired. As a result, stocking will be terminated in this LTRZ. Assessment Commercial catch sampling will be a priority and will target 200 lake trout biological samples and 50 CWT recoveries per year in this LTRZ. Offshore index assessment netting should be conducted in 2013 and 2014 to determine the status of lake trout at Point Clark. These surveys are particularly important given the recommended cessation in stocking. Pending results from these surveys, spawning surveys using large-mesh gillnets should be conducted in 2016 and 2017 to determine the status of the spawning population in this zone. Management Progress towards rehabilitation appears to have been made in recent years in this LTRZ. However, uncertainty regarding overall lake trout abundance in this zone suggest that the use of live-capture gear (trap nets), or gill-nets modified to reduce incidental catches of lake trout, should be encouraged in the commercial fishery. This could be facilitated by exploring the concept of incentives when using these alternative gear types to reduce mortality rates. Bottom substrates and bathymetry appear to be similar to other areas of the main basin where commercial trap nets are fished effectively suggesting that trap nets may be a viable option in this zone. These measures, if implemented, could substantially alleviate mortality rates, not only in this zone but in adjacent rehabilitation zones in Michigan waters, including Yankee Reef and Six Fathom Bank Refuge. Alternatively, restrictive management actions may be required to ensure lake trout annual mortality rates are kept below 40%. 23

83 LAKE TROUT REHABILITATION ZONE 12 Lake Trout Rehabilitation Zone 12 encompasses the western shores of the Bruce Peninsula with Chiefs Point at its southerly extent (Figure 12). This area includes the Fishing Islands, a stretch of small islands, reefs and shoals which provide abundant lake trout spawning habitat close to the deepwater habitat of the main basin. Figure 12. The revised boundaries of LTRZ 12, lake trout spawning shoals and depths greater than 40 fathoms. Overview and Progress to Date A substantial commercial fishery exists in this LTRZ. While the dynamics of the commercial fishery changed between 1990 and 2000, it remains relatively large, targeting primarily lake whitefish, with limited fishing for deepwater chub and walleye. Recreational fisheries, focused mostly on non-native salmonids, have also developed over the past 20 to 25 years in the vicinity of this LTRZ. This zone was assigned a deferred status in the 1996 Plan due to the large gillnet fishery. As a result, stocking has not been conducted in this zone. However, proportions of wild fish in fisheries independent surveys have increased substantially in this LTRZ and are now over 50%. Since 2007, mean ages have been older than the mean age to maturity and since 2008, sea 24

84 lamprey wounding rates have been below the threshold. Total annual mortality rates from lake trout caught in fisheries independent surveys have been below the threshold value since As is the case in a number of other zones, CUE targets have not been met on a consistent basis. Progress towards lake trout rehabilitation appears to be positive in this LTRZ although uncertainty remains regarding overall lake trout abundance. This zone may be approaching attainment of the short-term objective even though stocking has never been conducted. Stocking Increasing numbers of unclipped fish in assessment surveys indicate that stocking may not be required to achieve rehabilitation objectives in this zone. Stocking will not be conducted in this zone as a result. Assessment Independent index netting is currently conducted in the southern portion of this LTRZ on a yearly basis and indicates that numbers of unclipped fish have been steadily increasing in recent years. To confirm these results more widely within the zone, this survey should continue on a yearly basis and should include netting locations farther north in this LTRZ. Additionally, opportunities for enhancing the number of CWT returns from the commercial fishery in this zone should be investigated. This will provide information on the origin of immigrating lake trout. Management Commercial exploitation of lake whitefish in this zone has declined in recent years and as a result, lake trout catches and mortality have also declined. However, catch rates are consistently below targets even though other metrics suggest positive progress. The use of live-capture gear (trap nets), or gill-nets modified to reduce incidental catches of lake trout, should be encouraged in the commercial fishery to facilitate increases in lake trout abundance and to protect wild fish that have been observed in this LTRZ. This could be facilitated by exploring the concept of incentives when using these alternative gear types to reduce mortality rates. Bottom substrates and bathymetry appear to be similar to the areas of the main basin where commercial trap nets are fished effectively suggesting that trap nets may be a viable option in this zone. Alternatively, restrictive management actions may be required to ensure lake trout mortality rates are kept below 40%. 25

85 LAKE TROUT REHABILITATION ZONE 13 Lake Trout Rehabilitation Zone 13 is located in the area that separates the main basin from Georgian Bay, known as the Bruce Archipelago. The Bruce Archipelago is the northward extension of the Niagara Escarpment and is characterized by numerous islands, reefs and shoals stretching from the tip of the Bruce Peninsula north to Fitzwilliam Island (Figure 13). The zone contains several historic lake trout spawning locations as well as deepwater habitat in both the main basin and Georgian Bay. Fathom Five National Marine Park is also located in the southern section of this LTRZ. Figure 13. The revised boundaries of LTRZ 13, lake trout spawning shoals, depths greater than 40 fathoms, Fathom Five Marine Park boundaries as well as existing and proposed stocking sites. Overview and Progress to Date Small commercial and recreational fisheries exist in this LTRZ. Commercial fisheries traditionally targeted deepwater chub in the northern sections of this LTRZ with some limited lake whitefish effort and harvest. Changes in the commercial fishery and the decline of deepwater chub populations have resulted in more lake whitefish effort and harvest in recent years. Recreational fisheries in the area target non-native salmonids, and to a lesser extent, lake trout. 26

86 Stocking of pure-strain lake trout started in 1990 in this LTRZ and since 2000, stocking densities have been above the old stocking target density of 2.5 yearlings/ha. In the past lamprey-induced mortality did not appear to be inhibiting lake trout rehabilitation in this LTRZ, however wounding rates in 2010 were two to three times higher than the threshold. Wild fish are present in very low numbers in this LTRZ with catch rates in the commercial fishery and fisheries independent surveys well below target levels. Mean ages are below the mean age to maturity. Mortality rates have only been calculated twice since 1996 and as a result little is known about mortality in this LTRZ. However, the severely truncated age distribution and the lack of mature fish suggest that high mortality rates are experienced by adult and sub-adult lake trout and are preventing this LTRZ from reaching the short-term rehabilitation objective. Despite the fact that large numbers of unclipped lake trout have been stocked in this LTRZ as part of an early life stage stocking experiment (at the eyed egg, fry and fingerling life stages that preclude marking), unclipped adult lake trout have been virtually absent in subsequent surveys and commercial catch monitoring. Stocking To test the performance of Iroquois Bay strain lake trout in different habitats types, this strain should be stocked in this LTRZ if hatchery capacity allows. If Iroquois Bay strain fish are not available, Michipicoten strain can continue to be stocked in this zone. Stocking should be conducted at the new target density of 4.5 yearlings/ha (218,106 fish). The bulk of the spawning habitat in this LTRZ is present in the northern portions of the zone and fish should be stocked in close proximity to this habitat rather than at traditional shore stocking locations in the southern portion of the LTRZ. This will necessitate boat stocking at new sites (Figure 13) rather than shore stocking in Tobermory as is currently done. Assessment Limited information is available regarding the status of lake trout in this LTRZ. The stocking history suggests that a spawning survey might be appropriate in this LTRZ but, with the lack of data to verify this assumption, spring surveys were conducted in 2009 and Initially, summer, offshore index style surveys were proposed for this LTRZ but catchability issues associated with algae infestation of nets during summer months preclude netting at that time of year. Catches were low in these surveys. FLIN style surveys should be conducted in 2015 and 2016 to determine if any progress has been made in this LTRZ. Efforts to increase commercial catch sampling and specifically, CWT returns, should also be made in this LTRZ. Management Mortality rates appear to have been excessive in this zone in the past. Due to these high mortality rates, the use of live-capture gear (trap nets), or gill-nets modified to reduce incidental catches of lake trout, should be encouraged in the commercial fishery. Alternatively, restrictive management actions may be required to ensure lake trout mortality rates are kept below 40%. 27

87 LAKE TROUT REHABILITATION ZONE 14 Lake Trout Rehabilitation Zone 14 is located along the southern shore of Manitoulin Island in the main basin of Lake Huron (Figure 14). Extensive historical lake trout spawning shoals, abundant reefs and islands, as well as nearshore spawning habitat are all found in this zone. Abundant deepwater habitat is found to the immediate south of this LTRZ. This LTRZ is in close proximity to the Drummond Island Refuge, a heavily stocked area in Michigan waters where numbers of wild lake trout have been increasing in recent years. Figure 14. The revised boundaries of LTRZ 14, lake trout spawning shoals, depths greater than 40 fathoms and proposed stocking sites. Overview and Progress to Date The commercial fishery in this LTRZ targets mainly lake whitefish, with both gillnet and trapnet gear. A small amount of deepwater chub fishing has also historically occurred in this zone. There is a small recreational fishery in this LTRZ targeting non-native salmonids. This LTRZ was assigned a deferred status in the 1996 Plan due to high sea-lamprey-induced mortality in the past and the large commercial fishery in the LTRZ. As a result, no stocking of lake trout has taken place; however, immigration from U.S. waters is substantial. Sea lamprey wounding rates have declined to a large degree in this LTRZ (presumably due to control efforts 28

88 in the St. Mary s River) but have generally fluctuated between 5-10 wounds per 100 lake trout since Numbers of wild lake trout have increased dramatically since 2007 and now represent over 50% of the catch in the commercial fishery in this LTRZ. No fisheries independent assessment has been conducted in this LTRZ to evaluate lake trout abundance but catch rate data from the commercial fishery suggests that abundance is below target levels. Mean age of lake trout captured in the commercial fishery has fluctuated around the mean age to maturity since 2004 while mortality rates have been at or below the threshold since It is uncertain if this LTRZ has reached the short-term rehabilitation objective but it is clear that positive progress towards rehabilitation has been made in this LTRZ. Stocking Although the commercial fishery in this zone is still large, sea lamprey wounding rates have declined substantially in this LTRZ in recent years and as a result, a major impediment to rehabilitation has been minimized. It is recommended that stocking commence in this zone and should occur at a target density of 4.5 yearlings/ha (312,183 fish) using Seneca strain lake trout. Given the abundance of near-shore spawning habitat in this zone, shore stocking locations west of the Duck Islands should be used if possible. This area is in close proximity to the Drummond Island Refuge where lake trout stocked in this zone emigrating westward could be afforded some level of protection. Assessment Commercial catch sampling will be a priority and will target 200 lake trout biological samples and 50 CWT recoveries per year in this LTRZ. Sea lamprey wounding rates should also be closely monitored in this LTRZ given the past history of high wounding rates. Offshore index assessment surveys should be implemented for two years consecutively, starting four years after stocking commences (when the first cohort of stocked fish are five years of age). Pending no identification of major problems or impediments, spawning surveys using large-mesh gillnet gear should be implemented starting seven years after stocking commences (when the first cohort of stocked fish are eight years of age), for a two-year period, to verify the presence of a spawning population. Management Although stocking has not been conducted in this zone, wild fish now represent over 50% of the catch in the commercial fishery. As a result, the expanded use of live-capture gear (trap nets), or gill-nets modified to reduce incidental catches of lake trout, should be encouraged in the commercial fishery to promote survival of these wild lake trout. This could be facilitated by exploring the concept of incentives when using these alternative gear types to reduce mortality rates. The current use of trap nets in this zone indicates that they are a commercially viable means of capturing fish and their use could be expanded. Alternatively, restrictive management actions may be required to ensure lake trout mortality rates are kept below 40%. Such measures would also serve to benefit survival of lake trout immigrating from Michigan waters, including those originating in the Drummond Island Refuge. 29

89 LAKE TROUT REHABILITATION ZONE 15 Lake Trout Rehabilitation Zone 15, South Bay, is a bay on Manitoulin Island connected to the main basin of the lake by a constricted opening (Figure 15). South Bay has two sub-basins, one deeper, larger basin to the north and a smaller, shallower basin to the south. Ample spawning habitat and deepwater habitat have been identified in the inner basin of South Bay and also in the near shore areas of Lake Huron close to the mouth of the bay. Figure 15. The revised boundaries of LTRZ 15 and lake trout spawning shoals. Overview and Progress to Date Commercial fishing is not permitted within South Bay. However, commercial-style gillnets have been used intermittently in a First Nation subsistence fishery. This fishery has traditionally targeted both lake trout and lake whitefish. Recreational fisheries also exist within South Bay, targeting lake trout, non-native salmonids and smallmouth bass. Exclusive stocking of pure-strain lake trout started in this zone in 1992 and has generally been below the target of 2.5 yearlings/ha. However, rehabilitation of lake trout appears very encouraging in South Bay. Wild adults comprise a large proportion of the spawning population, nearly 100% in 2008, the number of age classes in the spawning population is above target 30

90 numbers and the mean age is regularly above the mean age to maturity. Catch-per-unit effort targets have been attained regularly and total annual mortality has always been below the threshold of 40%. Sea lamprey wounding rates have been very low in this LTRZ. These data suggest that the mid-term rehabilitation objective has been achieved. While the adult population exhibits characteristics of a successfully rehabilitated population, recent low recruitment of wild fish has raised concern regarding the status of lake trout in this LTRZ (Morbey et al. 2008). Continued assessment of this population is needed to ensure progress made to date is not compromised. Stocking Data gathered in South Bay suggests that natural reproduction has been occurring for a number of years and the mid-term objective has been achieved. Stocking will be terminated as a result and re-visited after additional assessment projects have been conducted to ensure that resumption of stocking is not necessary. Assessment Trap netting on the spawning grounds, FLIN surveys and creel surveys should be conducted every five years, for two consecutive years, to monitor the status of the lake trout population and the impacts of the fishery. The first cycle of assessment should start in Management Management of the recreational fishery in South Bay should emulate the management regime used in Parry Sound given the rehabilitation success observed there. This includes restrictive catch and possession limits and a maximum size limit to protect spawning aged fish. 31

91 LAKE TROUT REHABILITATION ZONE 16 Lake Trout Rehabilitation Zone 16, Six Fathom Bank, is located in the main basin of Lake Huron (Figure 16) approximately 55 km offshore. It straddles the international border between the State of Michigan and the Province of Ontario and is part of the Six Fathom Scarp mentioned in the LTRZ 11 section. Approximately one third of Six Fathom Bank is in Canadian waters. Spawning habitat has been identified on this reef along with significant amounts of deepwater in the immediate vicinity (Edsall et al. 1992). Figure 16. The revised boundaries of LTRZ 16 and depths greater than 40 fathoms. Overview and Progress to Date LTRZ 16 was identified in the 1996 Plan as an active zone with a primary protection classification. Since 1997, no commercial fishing activity has been allowed in Canadian waters of Six Fathom Bank shallower than 40 fathoms (73 m). There has been limited commercial fishing for deepwater chub in waters deeper than 40 fathoms to the east of the reef. The distance from shore limits recreational fishing activity within the LTRZ. Rehabilitation effort in the Ontario waters of Six Fathom Bank has been limited to restricting commercial activity. Stocking and assessment has been conducted by the Unites States Fish and 32

92 Wildlife Service (USFWS) and the United States Geological Survey (USGS) in Michigan waters of Six Fathom Bank. Beginning in the mid-1990s, a spawning population of hatchery adults has been observed on Six Fathom Bank, as have low numbers of wild juvenile lake trout. Up until recently, wild adult lake trout were not observed in fall spawning assessments conducted on Six Fathom Bank. However beginning in 2004, wild lake trout have represented approximately 25% of the fish captured in fall surveys. This increase in numbers of wild lake trout coincided with a lake-wide decline in alewife abundance. It appears that LTRZ 16 has achieved the short-term objective however, it is uncertain if the mid-term rehabilitation objective has been reached. Stocking Recent catches of wild fish on Six Fathom Bank suggest that the current stocking hiatus should be maintained. Future stocking events, if they do occur, will likely be initiated by United States (U.S.) agencies; Ontario stocking events are unlikely due to the distance from any ports. Assessment Assessment on Six Fathom Bank is conducted on a yearly basis by the USFWS using a vessel much larger than OMNR currently uses. These yearly assessment activities should be maintained. The distance from any ports is a major impediment to any Ontario contributions to assessment efforts on Six Fathom Bank. Management The current exclusion of commercial fishing activity in Ontario waters shallower than 40 fathoms (73 m) on Six Fathom Bank should be maintained. 33

93 LAKE TROUT REHABILITATION ZONE 17 Lake Trout Rehabilitation Zone 17 is a new rehabilitation zone located in the main basin of Lake Huron (Figure 17). This zone is focused on a number of reefs that rise out of deep water west of the Bruce Peninsula (Figure 17). These areas have been examined through the use of a remotely operated vehicle; this examination suggested that these areas may provide suitable spawning habitat for lake trout, particularly lake trout strains collectively referred to as humpers due to their spawning on submerged offshore mounds (Hansen 1996). As this is a new LTRZ, stocking and lake-trout-specific assessment have not occurred in this zone to date. Figure 17. The proposed boundaries of LTRZ 17, suspected lake trout spawning shoals, and depths greater than 40 fathoms. Stocking The review of the 1996 Plan suggested that a LTRZ focused on deepwater or reef type habitats as an area for reestablishment of deepwater forms of lake trout was lacking. Lake trout utilizing these types of spawning habitats are thought to augment genetic diversity which may help facilitate rehabilitation on a lake-wide basis. However, lake trout strains currently available in the OMNR fish culture system are all shallow-water spawning forms, collectively referred to as leans. These strains are not expected to spawn on the deep reef habitats present in LTRZ 17. To take full advantage of the spawning habitat in this LTRZ and meet the objectives of this 34