FISHERY MANAGEMENT. Table of Contents

Transcription

1 FISHERY MANAGEMENT Table of Contents Lake Trout (Cold Water) Fishery Warm & Cool Water Fishery Broad-scale Monitoring Appendix Eagle Lake Property Owners`Association

2 2 Fish & Fishery Table 1. Weight class distribution (by percent) for Lake Trout in gill netting at Eagle Lake in 1999 FISHERY MANAGEMENT A. Lake Trout (Cold Water) Fishery What is the status of the cold water fishery and can the Lake Trout fishery be sustained or even enhanced at Eagle Lake? Previous studies and information, as noted below, provide some information to address questions related to the status of the Lake Trout population at Eagle Lake. However, additional professional activities and advice, as well as volunteer assistance, are required in order to ensure a healthy Lake Trout fishery. Weight Class (grams) Percent (n=54) < > that point [Reference 1]. These recommendations have not materialized. SLIN netting in 1999 also allowed an appreciation of the proportion of cold water fish species at Eagle Lake (Figure 1), with Lake Herring (Cisco) making up the largest number. Background and Historical Data: 1. Stocking record Eagle Lake has been stocked with Lake Trout on 49 occasions since In the 10-year period from 1985 to 1994, 4000 to 8000 juvenile trout were introduced annually. The Ontario Ministry of Natural Resources & Forestry (OMNRF) has not stocked the lake since Spring Littoral Index Netting (SLIN) In the spring of 1999, a gill net assessment of the Lake Trout population at Eagle Lake authorized by OMNRF was carried out at 30 randomly chosen, but widely distributed sites [Reference 1]. Nets were placed perpendicular to the shoreline, so that the temperature at the top of the net was not greater than 13 C, ensuring that net placement occurred in the stratum optimal for Lake Trout. A total of 54 Lake Trout were caught and all but one of these was a stocked fish. As is evident in Table 1, the catch at Eagle Lake was heavily weighted towards relatively younger, smaller Lake Trout. The bulk of this population with 80 percent less than 900 grams (two pounds) likely resulted from the last stocking in Based on the results of this netting, it was recommended that stocking be reintroduced to Eagle Lake to historic levels (about 6,000 per year) for a period of at least four years, and that Lake Trout populations be reassessed at Figure Previous creel surveys Winter surveys, primarily to assess Lake Trout catches at Eagle Lake, were held over eight days during a 3-week period in February 1981 and over nine days for a similar period in During the 1981 survey, 75 Lake Trout were caught, with 77 percent stocked fish. During the 1982 winter survey, 126 Lake Trout were caught (89 percent stocked fish). Both the significant proportion of stocked fish caught both years and the considerable time spent to catch Lake Trout indicate poor recruitment of juvenile Lake Trout. It should be noted that due to the precarious status of Lake Trout populations in many southern Ontario lakes, including Eagle Lake, and the high susceptibility of Lake Trout to winter angling, the winter fishery for Lake Trout is now closed in many of these lakes. State of the Lake Report Update 2015

3 3 Staff from OMNRF organized a stratified angler survey in 2010 that spanned the period May 22nd to September 6th. This creel survey involved interviews and observations of fishing boats over a 3-hour period during each of 20 selected days and times. Only a small number of anglers who were interviewed were actually fishing for Lake Trout and none were caught during this survey. Because fishing for Lake Trout during the winter months is now prohibited at Eagle Lake (except for First Nations), there has been some concern that Lake Trout were illegally being kept during the ice fishing season. The local OMNRF conservation officer, however, confirmed that sporadic, unannounced visits to Eagle Lake during the winters of 2014 and 2015 found no significant poaching of Lake Trout at Eagle Lake. 4. Shoal rehabilitation Lake Trout are fall spawners, with spawning occurring over large boulder or rubble bottoms, normally in depths less than 15 meters. With time, portions of spawning shoals can become devoid of large rocks or silt can accumulate between the rocks. This means that at the time of egg laying in the fall, individual eggs are exposed and may be eaten by other fish and crustaceans. Rehabilitation of such shoals can be one approach to increase native Lake Trout populations. Rehabilitation consists of transporting washed local rock, about three to six inches in diameter, to suitable areas of shoals used by Lake Trout for spawning and dumping these to produce sufficient interstitial spaces to provide protection from predators and allowing for successful egg incubation (Figure 2). The eggs remain in their rocky incubator over winter until their hatching early the following spring. On August 17, 2006, using a barge for transport, approximately 50 tons of stone were shoveled onto the preselected areas of the shoals. To inspect the extent and depth of rock deposited, underwater pictures were taken to compare with photographs taken prior to adding the rock to the shoals. OMNRF required direct observation that Lake Trout were continuing to use the shoals for spawning. So one night early in November 2007, an Eagle Lake resident drifted over two locations on the shoals and with the aid of a bright light directly observed numerous Lake Trout congregating there. 5. Lake Trout spawning site survey On September 15, 2014, OMNRF biologists from the Kingston office checked multiple regions of Eagle Lake as part of a lake survey for potential Lake Trout spawning sites (Figure 3). With the exception of the large shoal off of Camp Oconto, most other shoal sites were unsuitable, as were shorelines at the west end of the lake and the westerly side of Opeongo Point. However, a few potentially suitable sites were identified along the north shore and along shoreline areas at both Shoal Island and the unnamed island adjacent to Shoal Island (Figure 4). Figure 3. OMNRF staff checking out potential Lake Trout spawning sites on the north shore of Eagle Lake in September In late July 2006, an OMNRF fish management biologist visited Eagle Lake and gave approval for three locations on the extensive shoals near Camp Oconto for a Lake Trout rehabilitation project. Figure 2. Shovelling piles of rock onto the shoals near Camp Oconto in Figure 4. Potential or know Lake Trout spawning sites at the norht end of the lake designated by OMNR for checks of fall spawning activity. Site #2 is the previously rehabilitated shoal offshore from Camp Oconto. Eagle Lake Property Owners`Association

4 4 Fish & Fishery Following this visit to the lake, one night in early November 2014 when the water temperature had dropped to about 10 degrees C (ideal spawning conditions), OMNRF staff surveyed the rehabilitated shoal (site 2 in Figure 4) and observed 38 Lake Trout congregated there, presumably spawning. For additional observations of Lake Trout spawning activity, OMNRF staff again visited Eagle Lake on two occasions during the night, one in late October and the other in early November 2015 when water temperature ranged from 10.8 to 11.8 degrees C. Using a lighted, video-capable underwater camera, at depths between 1 to 2.5 metres, over 50 spawning Lake Trout were observed at the rehabilitated shoals off Camp Oconto (site #2 in Figure 4). A small number of Lake Trout were also seen at what were considered two other potential spawning areas (sites #1 and #4 in Figure 4). At site #2, three male Lake Trout were netted (Figure 5) to obtain weight (4 to 4.5 kilograms or 9 to 10 pounds) and length measurements, check whether sperm were present or had been released, collect scales for age determination, and then placed back in the lake. profiles from 2002 to 2009 that were published in our State of the Lake Report and an additional 16 for 2010 to 2014 (see the appendix of the Eagle Lake Water Quality section of the State of the Lake Report, Update 2015, Part 1). Optimal habitat for adult Lake Trout has a dissolved oxygen concentration of 6 mg/l, although concentrations as low as 4 mg/l, can be tolerated. However, juvenile Lake Trout have a higher minimum dissolved oxygen requirement of 7 mg/l [Reference 2]. Data from May to late July/early August indicate adequate habitat for both adult and juvenile Lake Trout. For the interval from August 14 to September 30, of the 34 dissolved oxygen/temperature profiles available from 2002 to 2014 at Eagle Lake, 11 are from this time span (Figure 6). This data suggests that Lake Trout habitat is inadequate to borderline in some years, e.g., 2002, 2006, and 2009 to In other years, e.g., 2003, 2007, 2012, 2014 and 2015, habitat conditions in the late summer are acceptable for Lake Trout. Based on such dissolved oxygen/temperature profiles, it seems that every 4 to 5 years there is sufficient dissolved oxygen, i.e., a minimum of 7 mg/l, in portions of the water column to support juvenile Lake Trout (Figure 6). These findings suggest that it is the late summer dissolved oxygen/temperature profiles that may be a limiting factor affecting the adequacy of the lake environment for Lake Trout, particularly juvenile fish. Nonetheless, there is potential for survival of a proportion of juvenile fish in certain years. So some degree of recruitment for the adult pool of Lake Trout at Eagle Lake seems probable. This conclusion is further supported by a calculation to classify Lake Trout lakes as a medium- to highly-sensitive Figure 5. OMNRF staff members Graham Branscombe (above) and Justin Punchard (below) holding Lake Trout netted at shoal site #2 for data collection prior to release. 6. Water Quality Data Analysis at Eagle Lake As part of the Watershed Watch Program, Rideau Valley Conservation Authority staff have collected dissolved oxygen/temperature profiles at the deep point on a regular basis. A total of 34 profiles are available for analysis; 18 Figure 6. For each year with data available, the light blue zone represents the portion of the usable lake depth as lake trout habitat, the light red zone as optimal habitat with up to 7 mg/litre of dissolved oxygen. Usable habitat for lake trout is defined as less than 15.5 C and 4 mg/l or more of dissolved oxygen. Optimal habitat is defined as less than 10 C and 7 mg/l or more of dissolved oxygen. State of the Lake Report Update 2015

5 5 habitats for this species referred to as MVWHDO (mean volume weighted hypolimnetic dissolved oxygen). In the deep cold-water levels, a minimum value for this calculation of 7 mg/litre is required. As noted above, this level of dissolved oxygen was chosen because experimental evidence indicates that survival of newly hatched and year-old Lake Trout is poor at levels less than this amount. As is evident in Figure 7, this standard or close to it was reached in Eagle Lake in 2003, 2007 and 2012 [References 2 and 3]. Figure 7. MVWHDO calculated from observed dissolved oxygen profiles in various years at Eagle Lake. Note that in 2003, 2007 and 2012, values approached or reached 7 micrograms/litre of dissolved oxygen confirming adequate lake trout environment in late summer for those years [Reference 3]. deeper cold water zone preferred by Lake Trout, has affected newly hatched and juvenile Lake Trout at Eagle Lake. The latter have considerably higher requirements of dissolved oxygen compared to adult Lake Trout. So, the amount of dissolved oxygen in the water column, particularly in late summer (detailed in section 6 above), determines the degree of annual survival of each year s Lake Trout hatchlings, information lacking in determining the current ratio of natural to stocked Lake Trout at Eagle Lake. 8. Potential effects of climate change on Lake Trout fishery If, as a result of climate change, surface water temperatures in the fall should rise by even a few degrees, this could seriously affect Lake Trout populations. For Lake Trout, egglaying in late October to early November is triggered by daylight length not water temperature. Under normal circumstances, eggs remain dormant over winter and, as the water warms in early spring, begin to develop and eventually hatch. If, however, surface water is warmer than expected at spawning, newly laid eggs will start to develop only to be killed as water temperatures cool prior to the lake freezing over. Experimental evidence supports this scenario [References 5 and 6] with dire consequences for recruitment of juvenile trout (Figure 8). There is little direct information explaining the poor oxygenation of the deep water at Eagle Lake. Factors might include inadequate "turnover" of lake water in the spring of certain years, variable and fluctuating algal concentrations, nutrient loads, the lake morphology at Eagle Lake or climactic conditions [Reference 5]. This aspect needs further investigation. 7. Lake Trout Assessment Action Plan A more accurate estimate of the overall Lake Trout population at Eagle Lake is required, but especially the numbers and size range of young natural, i.e., non-stocked, Lake Trout. It is planned to accomplish this with a netting protocol referred to as SPIN (Summer Profundal Index Netting) during July and August 2016 by OMNRF staff [Reference 4]. This is accomplished by random placement of gill nets that provides an equal distribution of nets over the entire lake. Nets are also placed at a series of preset depths, especially in the core strata of 10 to 40 metres. SPIN protocol is designed to obtain a Lake Trout sample as representative as possible for the current Eagle Lake population. The target is 75 or more Lake Trout [Reference 3]. SPIN assessment has the potential to provide information relative to the adequacy of the spawning shoals, but especially how the crucial level of dissolved oxygen in the Figure 8. The hatched regions reflect the gradual decline in egg and juvenile lake trout survival with increasing lake water temperature, but a similar gradual increase in survival for a warm-water fish such as bass [References 5 and 6]. Other studies suggest that in the future, climate change could result in a significant impacts on Lake Trout habitat [Reference 7], particularly at the southern limits of their geographic range. As a result, in some southern Ontario lakes, extinction of Lake Trout may be inevitable. B. Warm and Cool Water Fishery 1. What is the current status of the warm/cool water fishery at Eagle Lake? As detailed below, current information indicates that the species of most interest, Smallmouth Bass, Largemouth Eagle Lake Property Owners`Association

6 6 Fish & Fishery Bass (warm water species) and Northern Pike (cool water species), have sustaining populations at Eagle Lake. 2. Creel survey Fishing activities at Eagle Lake are mainly directed at Smallmouth and Largemouth Bass, as well as Northern Pike. As mentioned in Section A, part 3 above, staff from OMNRF organized a stratified angler survey in 2010 that spanned the period May 22nd to September 6th. This involved interviews and observations of fishing boats over a 3-hour period on each of the 20 selected days. Fishing at Eagle Lake for these species was considerable [Reference 8]. Over 50 percent of the fishing effort at Eagle Lake was directed at Smallmouth and Largemouth Bass and not surprisingly, bass accounted for the largest number of fish caught and retained, 4032 and 384, respectively, during this creel survey. A respectable, but considerably lesser number of Northern Pike (256) were caught, with about 7 percent retained during this survey. This creel survey suggests healthy, self-sustaining populations of these species at Eagle Lake. 3. Climate change In gauging the potential effects of future climate change for the warm/cool water fishery, it is noteworthy that in 2013, the OMNRF opened the bass fishing season one week earlier in our zone, as well as extending the season by two weeks until December 15th [Reference 9]. As noted in the summary for this bulletin [Reference 9], "Bass populations in southern Ontario have responded favourably to a trend toward a warmer climate. The early arrival of spring warming means that bass are spawning earlier, and longer growing seasons increase the growth and survival of bass, particularly in their first year." Research also supports warmer shoreline water temperatures even a 1 to 3 degree C increase leading to a more abundant population of both species of bass in the future [Reference 5]. As well, the longer growing season will eventually result in an increased likelihood of catching larger specimens. C. Broad-scale monitoring This program, initiated by the OMNRF in 2008, will assess the health of fish populations by conducting netting surveys, carrying out creel surveys and collecting water quality information across a broad geographic area [References 10 and 11]. In Southern Ontario this program will sample 255 or about 5 percent of the lakes on a fixed or variable schedule. Lakes with a fixed designation, such as Eagle Lake, will be monitored every five years. A variety of information will be recorded from the fish caught during the netting surveys, including fish species, sex, age, length, weight, reproductive capacity and general health. For Lake Trout, age determination will be done using the inner ear otolith (calcium carbonate structures for equilibrium with tree-like annual layers that can be counted microscopically). Creel surveys will provide information related to angling pressure and success rates, while water quality sampling will give an indication of overall health of the lake environment. In July 2008, MNRF technicians undertook the initial broad-scale monitoring (BSM) at Eagle Lake over a 3-week period. This consisted of anchoring large and small mesh gill nets at various locations and at differing depths, each for a 24-hour period. Nets were then retrieved and fish caught in the net collected for later identification and analysis. In 2008, a total of 32 sites were surveyed at Eagle Lake which netted 875 fish of 13 different species (Table 2). Of the five Lake Trout netted (4 stocked and one natural), one was 25 years of age based on the otolith data available for these Lake Trout. The second round of gill netting was carried out at multiple sites at Eagle Lake from September 3 to 11, 2014 by OMNRF employees, Kraig Kavanagh and Aaron Owens (Figure 9). In this round of netting, 701 fish were caught from 30 sites (Table 2). Although no Lake Trout were netted on this occasion, one additional species, Bluntnose Minnow, was obtained. Comparing the sport fish Smallmouth Bass, Largemouth Bass and Northern Pike reveals no significant change in this population, as these three species account for 10.7 percent in 2008 and 11.0 percent Unfortunately, general warming of the lake water will likely negatively effect Northern Pike, a cool water fish [References 5 and 6]. For more details on the influence of climate change on the fishery, see the section devoted to Climate Change later in this report. Figure 9. OMNRF staff retreiving a small-mesh net anchored for 24 hours off a small island at Eagle Lake in September State of the Lake Report Update 2015

7 7 Table 2. Broad-scaling monitoring (fish netting) results at Eagle Lake for 2008 and No. of nets set Fish Species No. Percent No. Percent Smallmouth Bass Largemouth bass Northern Pike Lake Trout Lake Herring Lake Whitefish Yellow Perch Bluegill Pumpkinseed Rock Bass Brown Bullhead Yellow Bullhead White Sucker Bluntnose Minnow Unidentified Totals in 2014 (Table 2). In fact, as evident in Table 2, the only major difference between these BSM nettings is that fewer Yellow Perch were sampled in the second round (158 in 2008 compared to 79 in 2014). Lake Herring (Cisco) continues to account for the largest population of fish at Eagle Lake (Table 2). A PDF file of the results of broad-scale monitoring at Eagle Lake in 2008 has been produced by OMNRF [Reference 11] and is available in the Appendix (a similar report for the 2014 fish assessment will eventually be available). References: 1. Ontario Ministry of Natural Resources (1999). Snetsinger, R: The 1999 Spring Littoral Index Netting for Lake Trout in Eagle and Loughborough Lakes. 2. Evans, DO (2007). Effects of hypoxia on scope-for-activity of Lake Trout (Salvelinus namaycush). Can. J. Fish Aquat. Sci. 64(2): Morikawa DS, Boegman L (2014). Impact of lakeshore development on Lake Trout habitat in a Canadian Shield lake. Fund. Appl. Limnol.(Submitted). 4. Sandstrom, S. J. and N. Lester Summer Profundal Index Netting Protocol; A Lake Trout Assessment Tool. Ontario Ministry of Natural Resources. Accessed January ( 5. Casselman JM (2002): Effects of temperature, global extremes, and climate change on year-class production of warmwater, coolwater, and coldwater fishes in the great lakes basin. American Fisheries Society Symposium 32: Casselman JM (2012). Climate change and eastern Ontario fish populations: Driving environmental factors and shifting baselines; What to expect, how to adapt. Lake Links Workshop, Perth, ON. 7. Minns CK, Shuter BJ, McDermid JL (2009): Regional Projections of Climate Change Effects on Ontario Lake Trout (Salvelinus namaycush) Populations. Climate Change Research Report, CCRR 14, OMNR. 8. Eagle Lake: State of the Lake Report (2011), Parham, Ontario, County of Frontenac, pages 42 and Ontario Ministry of Natural Resources (2013b). PDF Bulletin: Changes to Bass Seasons in Southern Ontario (Zones 17, 18 and 20). 10. Bendig A (2009). Broad Scale Monitoring of Ontario's Inland Lakes. Lake Links Workshop, Perth, ON. 11. Ontario Ministry of Natural Resources (2013a). Fish online website (accessed January 2016) ( PublicDocs/EN/Policy/LakeBulletinReport-EN- Eagle_Lake-Zone18-Cycle Contributions and Review by: Steve Burgess Irv Dardick Monique Charette Graham Branscombe Justin Punchard Hayden Piper Eagle Lake Property Owners`Association

8 8 Fish & Fishery APPENDIX Broad-scale Fisheries Monitoring Bulletin EAGLE LAKE - ZONE 18 Eagle Lake Facts Township(s): Olden and Hinchinbrooke Surface Area: 641 ha Maximum Depth: 35.4 m Average Depth: 12.1 m Fish Netting Results Fish populations were surveyed using large and small mesh nets to provide information on fish species present and their characteristics, such as growth, age and abundance. The catch data below show that 13 species were surveyed in large mesh nets. No additional fish species were observed in small mesh nets. Water Clarity: 4.0 m Monitoring Activities Fish netting Fish contaminants Zooplankton Water chemistry Bathymetry Water temperature/dissolved oxygen Aquatic invasive species Netting Summary Netting period: July 02-15, 2008 Number of net sets: 29 Fish species Total Catch % Maximum Length cm Minimum Length cm Average Length cm Cisco Largemouth Bass Bluegill Rock Bass Yellow Perch Lake Whitefish Smallmouth Bass Northern Pike Brown Bullhead Pumpkinseed Lake Trout Yellow Bullhead < White Sucker < Number of fish species caught: 13 About the Program The Broad-scale Monitoring Program provides information for managing our fisheries effectively. This bulletin provides a snapshot of the recent monitoring activities and netting results. Netting is conducted using large and small mesh nets to understand the characteristics of fish communities in a lake. Large mesh nets contribute information about fish species and small mesh nets describe the fish community. To learn more about the sampling program visit Fish Ontario: Monitoring and State of the Resource Reporting. Proportion of Fish Caught in Large Mesh Nets Cisco Largemouth Bass Bluegill Other Rock Bass Lake Whitefish Yellow Perch ontario.ca/fishing State of the Lake Report Update 2015