Moses Lake Fishery Restoration Project

Transcription

1 Moses Lake Fishery Restoration Project Factors Affecting the Recreational Fishery in Moses Lake Washington Annual Report April 2007 DOE/BP

2 This Document should be cited as follows: Burgess, Dave, Katrina Simmons, Rochelle Shipley, Tammy Gish, "Moses Lake Fishery Restoration Project; Factors Affecting the Recreational Fishery in Moses Lake Washington", Annual Report, Project No , 42 electronic pages, (BPA Report DOE/BP ) Bonneville Power Administration P.O. Box 3621 Portland, OR This report was funded by the Bonneville Power Administration (BPA), U.S. Department of Energy, as part of BPA's program to protect, mitigate, and enhance fish and wildlife affected by the development and operation of hydroelectric facilities on the Columbia River and its tributaries. The views in this report are the author's and do not necessarily represent the views of BPA.

3 Factors Affecting the Recreational Fishery in Moses Lake, Washington FY 2004 Final Annual Progress Report Reporting Period September 26, 2004 October 1, 2005 Project Number: Contract: Prepared for Submission to the Bonneville Power Administration

4 Acknowledgments We would first like to thank the Bonneville Power Administration (BPA) for funding the Moses Lake Project. More specifically, we would like to acknowledge our COTR, Greg Baesler for his assistance and efforts. We would also like to thank members of the Washington Department of Fish and Wildlife Region 2 staff for their logistical and often technical support. We would like to thank members of the community, especially Ron Sawyer and members of the Columbia Basin walleye club and Columbia Basin Bass Club for their efforts and support. Specifically, we would like to thank Kyle Curtis, Gert Trout and Gary Mane for all their help with entrainment and avian predator data collections. We would also like to thank the members of the Banks Lake Project, Matt Polacek, Aulin Smith and Josh McLellan for their assistance during our sampling efforts. During the tenure of this project we have also had the pleasure of working closely with Dr. David Bennett and Jeff Korth. Their guidance, direction and constructive criticism and multiple edits of our work was much appreciated and integral in our operations. Moses Lake Project Staff Dave Burgess Katrina Simmons Rochelle Shipley Tammy Gish Moses Lake Project Support Staff Jeff Korth, WDFW district biologist/bpa contact Dr. David Bennett, University of Idaho, advisor ii

5 Table of Contents Section Page I Background...1 A Abstract...1 B Overall Project Goal...4 II Phase II - Management and Evaluation...5 A Objective 1. Quantify sources of mortality determined in Phase I as responsible for fish community changes Task Quantify annual entrainment losses from Moses Lake Task Identify significance of avian and fish predation...7 B Objective 2. Refine management direction based on current information from Phase I investigations Task Application of modeling technology to augment understanding of the Moses Lake fishery Task Carp isolation and removal...26 III Conclusion...30 IV Literature Cited...32 iii

6 List of Tables Table Table 1. Page Summary of entrainment from at the Moses Lake Irrigation District outlets and the United States Bureau of Reclamation Dam on Moses Lake, Washington...7 Table 2. Grams of prey items consumed by 1,000 walleye from February 11, 2005 to March 2, 2005, in Moses Lake, Washington...14 Table 3. Summary of avian piscivorous foraging behaviors on Moses Lake, Washington from February 2005 through May iv

7 List of Figures Figure Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Page Logic tree for Phase I of the Moses Lake Project...3 Logic tree for Phase II of the Moses Lake Project...4 Screw trap deployed at the United States Bureau of Reclamation Dam on Moses Lake, Washington...7 Fan boat used to move across ice and deploy gillnets in Moses Lake, Washington...10 Diet composition of juvenile walleye captured in Moses Lake, Washington during winter and early spring Diet composition of adult walleye captured in Moses Lake, Washington during winter and early spring Proportion of fish in the diets of 1,000 walleye during winter and early spring in Moses Lake, Washington based on bioenergetics modeling...14 Total species composition of avian predators on Moses Lake, Washington between October 2004 and July Monthly abundance of gulls on Moses Lake, Washington between October 2004 and July Monthly abundance of grebes on Moses Lake, Washington between October 2004 and July Monthly abundance of double-crested cormorants on Moses Lake, Washington between October 2004 and July Monthly abundance of common mergansers on Moses Lake, Washington between October 2004 and July Counts of common mergansers on Moses Lake, Washington during the month of December from Areas encompassed by an oval have been identified as ideal locations to install carp exclusion barriers in Moses Lake, Washington...29 v

8 Figure 15. Carp exclusion barrier on Moses Lake, Washington constructed by the Moses Lake Irrigation district...30 vi

9 I. Background. A. Abstract. Dam construction and the resulting loss of anadromous fish stocks to central Washington placed greater importance on resident sport fishes, especially in central Washington. Shortly after dam construction on the Snake and Columbia rivers, Moses Lake was the premier fishery for resident fishes in central Washington, including black crappie (Pomoxis nigromaculatus), bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), and yellow perch (Perca flavescens). Beginning in the late 1970s and throughout the 1980s, these fisheries experienced a gradual decline probably a result of several events including changes in species composition and abundance, overharvest, and changes in habitat conditions. To mitigate for lost recreational fishing opportunities, the Washington Department of Fish and Wildlife (WDFW) initiated several projects, including the supplementation of the population with black crappie brood stock in 1995 in the hopes of increasing production, and implementing a rainbow trout (Oncorhynchus mykiss) net pen rearing program. The most expansive effort, however, was a long-term survey begun in the early 1990s to assess the status of fisheries and changes to fish populations. In the late 1990s, the WDFW obtained funding from the Bonneville Power Administration (BPA) to assess factors affecting the Moses Lake fish community based on data obtained through sound objective, scientific assessment. The long-term goal of this work was the formulation of management recommendations that would enhance the sport fishery and economic benefit to the Moses Lake community and the state of Washington as mitigation for lost recreational fishing opportunities for anadromous species in the blocked portion of the Columbia River (Bennett et al. 2002). Phase I of the study was designed to partition the sources of mortality to target species [black crappie, bluegill, yellow perch, walleye (Stizostedion vitreum), rainbow trout, largemouth bass, and smallmouth bass (M. dolomieui)], culminating in identifying and ranking limiting factors by degree of impact to the fishery (Figure 1). This investigation has eliminated some of the possible negative impacts to the fishes of Moses Lake (e.g. productivity/competition issues, summer-fall predation issues, exploitation, and water 1

10 quality) and focused attention on a few selected factors that require further investigation [winter predation, entrainment, and impacts from carp (Cyprinus carpio)]. The current statement of work for FFY05 begins Phase II (Figure 2). Objective 1 includes investigating sources of mortality responsible for fish community changes as determined in Phase I. Specific tasks include evaluating the significance of annual entrainment losses from Moses Lake, and assessing avian and fish predation. Objective 2 includes the identification of the most feasible management actions based on current information from Phase I investigations. Specific tasks include modeling harvest strategy and entrainment influences, and identifying habitat enhancements and carp removal strategies. 2

11 Project Goal: Assess factors affecting the Moses Lake fish community. Partition the sources of mortality. Examine species interactions. Assess habitat quality and quantity. Assess the influence of angling. Assess the influence of predation. Quantify entrainment losses. Estimate the mortality of cohorts. Assess secondary production and its influence on interspecific interactions. Assess competitive interactions of target fishes. Assess impacts of carp. Monitor critical water quality parameters. Identify factors with the greatest impacts on the Moses Lake fish community. Identify data gaps suggested by the latest investigation. Identify the most feasible management actions based on the latest investigations in conjunction with fisheries managers. Figure 1. Logic tree for Phase I of the Moses Lake Project. 3

12 Evaluate the influence of selected factors affecting the Moses Lake fishery as determined in Phase I. Discern the appropriate management actions based on Phase I results. Quantify annual entrainment losses and assess the influence on the fish community. Assess the impacts of fish and avian predation on the fish community. Model mortality influences on stock abundance. Develop plans for carp removal and isolation from spawning areas. Implement and evaluate the role of the management actions on the sport fishery. Management actions are successful. Management actions are not successful. Continue to monitor and evaluate management actions. Reassess management actions in light of new information. Figure 2. Logic tree for Phase II of the Moses Lake Project. B. Overall Project Goal. The goal of this project is to identify factors affecting the Moses Lake sport fishery and implement a management plan (Phase II) with the aim of enhancing the sport fishing recreational opportunities and the economic return to the Moses Lake community and Washington State. 4

13 II. Phase II - Management and Evaluation. A. Objective 1. Quantify sources of mortality determined in Phase I as responsible for fish community changes. Task Quantify annual entrainment losses from Moses Lake. Task Identify significance of avian and fish predation. 1. Task Quantify annual entrainment losses from Moses Lake. a. Introduction. Results from Phase I strongly implicate entrainment losses as a major factor responsible for the decline of the sport fishery in Moses Lake (Table 1). Studies were only conducted at the Moses Lake Irrigation District (MLID) outlets (north outlets) and were primarily during drawdown. However, preliminary analyses suggested that the emigration of numerous juvenile game fish was a significant component of the total annual loss of some important species from Moses Lake. In addition, these losses were not necessarily proportional to the species relative abundance in the lake, and it was obvious that losses were higher for certain species. Species identified as major emigrates in Phase I coincide with those found in studies in the Midwest, Northeast, and Southeast (Winchell et al. 1997). Yellow perch and black crappie, two target species found in Moses Lake, were considered High to Moderate-High emigrates. Losses as high as 3.2 fish/10 6 ft 3 of water have been reported for black crappie and yellow perch. Our total estimated losses (~ total fish/10 6 ft 3 ) were considerably higher in Moses Lake, especially for black crappie, than those reported by Winchell et al. (1997). Random samples taken later during the fall/winter period further suggested that species entrainment composition and numbers might change drastically over the year. Even though water temperatures were near winter lows and flows were greatly reduced, fish emigration was highest during this period. In Phase I, fish emigration through the MLID outlets was primarily assessed during the fall/winter drawdown. Preliminary estimates of entrainment losses also may be dwarfed by the larger loss from the United States Bureau of Reclamation (USBOR) Dam (south outlets). A recent study conducted by the Washington State Department of 5

14 Ecology (DOE) estimated the average discharge through the USBOR Dam was 809 cubic feet/second (cfs) and 241 cfs during November 2002 and February 2003, respectively (Evans and Larson 2002). During fall and winter entrainment sampling, the mean discharge through the MLID outlets was 72.3 cfs and 8.3 cfs, respectively. Assuming a linear relationship between discharge and the number of fish entrained, initial results suggest a large number of fish may be entrained through the USBOR Dam. b. Methods. We assessed entrainment losses year-round through trapping at the United States Bureau of Reclamation (USBOR) Dam when flows were adequate to operate an eightfoot screw trap (Figure 3). Due to regional drought conditions and subsequent poor snow pack, USBOR operations were altered considerably, often there was negligible flow, and entrainment trapping could not be conducted. However, when adequate flows existed, a stratified random sampling design (seasonally, day and night) to quantify total fishes annually emigrating from Moses Lake was followed. Numbers of each species and size of fishes emigrating were quantified and expanded to estimate total emigration losses using a ratio estimator (number of fish/flow) (Scheaffer et al. 1996). c. Results and Discussion. A journal paper summarizing the entrainment results from will be submitted in lieu of a descriptive results and discussion portion of this report. However, a brief summary of our results from the USBOR outlets during this sampling year has been produced (Table 1). Similarly, to the previous years work on the MLID outlets, entrainment on the USBOR outlet was high. 6

15 Figure 3. Screw trap deployed at the United States Bureau of Reclamation Dam on Moses Lake, Washington. Table 1. Summary of entrainment from at the Moses Lake Irrigation District outlets and the United States Bureau of Reclamation Dam on Moses Lake, Washington. AM-PM combined data is a result of no significant difference between time periods. Month/Year Time Period Mean # Fish / m 3 Upper Bounds Lower Bounds (95%) (95%) November 2004 AM-PM combined December 2004 AM-PM combined January 2005 AM-PM combined April 2005 AM-PM April 2005 PM-AM May 2005 AM-PM May 2005 PM-AM Task Identify significance of fish and avian predation. a. Introduction. Phase I assessments indicated that over-winter and early spring survival of selected age 1 and 2 game fishes was a critical bottleneck. Diet data indicated that 7

16 consumption by fish predators is significant but probably does not account for the total loss. However, these data only included limited winter diet samples from piscivorous fishes. WDFW and United States Fish and Wildlife Service (USFWS) winter migratory bird counts show large numbers of birds occupy Moses Lake year-round (WDFW 2004). Many anglers believe avian predators are the major source of fish mortality, and that the primary culprit for the decline in the Moses Lake fishery is the double-crested cormorant (Phalacrocorax auritus). These are large birds and are quite visible as they often travel in large groups around Moses Lake. However, the common merganser (Mergus merganser) is the most abundant avian predator on Moses Lake (WDFW 2004). Both species are known to be highly piscivorous (Schramm et al. 1987; Roby et al. 1998; Major et al. 2002). Double-crested cormorants can consume a substantial number of fish at a rate of 20-25% their body weight/day (Glahn and Brugger 1995). A common merganser can consume up to 27% of its body weight a day (Canadian Council of Ministers of the Environment 1999). Waterfowl counts during December 2003 indicated numbers of common mergansers as high as 3,000/day. Therefore, if the mean weight of a common merganser is 1.5 kg, the potential loss to the Moses Lake fish community could be as high as 1,200 kg/day. Major et al. (2002) reported common mergansers consumed over 14,000 kg of fish in a 5-month period in the Yakima River. Common mergansers begin to migrate to Moses Lake during fall and stay through early spring, while double-crested cormorants arrive during early spring and stay through October. Although double-crested cormorants over-winter on the Pacific Coast, their presence in the early spring may result in significant juvenile fish losses in Moses Lake. Common mergansers are temporally segregated from double-crested cormorants as they are found on Moses Lake during the winter, therefore may be accounting for a portion of over-winter mortality to target fishes. The objective of this task was to determine the level of predation incurred by bird and fish piscivores on the fish community within Moses Lake via stomach content analysis. b. Methods. i. Fish Predators. 8

17 Winter sampling on Moses Lake has proven difficult due to ice cover. When Moses Lake was frozen, we used a fan boat in order to move across the ice safely and deploy gillnets (Figure 4). Walleye diets were collected during February and March 2005 at various locations on Moses Lake. The collection of diets from Moses Lake predators focused on walleye, as they are the most abundant predator. To obtain stomach samples, fish were collected using gillnets. Gillnets were set with the smaller mesh being deployed near shore and stretched perpendicular from the shoreline. Gillnets were deployed and checked within one net night. Whole stomachs were extracted from fish captured in gillnets as most fish were dead (nets were left in overnight and fish only removed once). Samples were strained and their contents preserved in 95% ethanol. Stomach items were identified to the lowest practical taxon using Leica x dissecting scopes, enumerated, measured, and weighed to the nearest g. For zooplankton identification, we used Pennak (1989) and for insect identification, we used Merritt and Cummins (1996). For fish identification, we used Hansel et al. (1988), Wydoski and Whitney (2003), WDFW internal diagnostic bone keys, and some collected voucher specimens to increase our level of confidence when bones were collected from the stomachs. Food items were weighed and the proportional contribution of major food items were determined. Predatory inertia was examined for each of the predator fishes similar to that of Stewart et al. (1981). Data were entered into a bioenergetics model to quantify fish consumption. 9

18 Figure 4. Fan boat used to move across ice and deploy gillnets in Moses Lake, Washington. ii. Avian Predators. Bird stomachs were to be collected by common sampling methods suited for specific species and food retention (Wood 1987; Major et al. 2002). Unfortunately, we encountered a substantial delay when applying for a permit to use lethal measures to collect double-crested cormorants and common mergansers. When the permit was finally granted, the WDFW did not approve as western grebes (Aechmophorus occidentalis) were on the permit. We reapplied for the permit and once granted, double-crested cormorants were no longer present on Moses Lake, and common mergansers were not on the permit. We were told we could collect common mergansers using a conventional hunting license. However, I have found that common mergansers are hard to collect using conventional hunting methods as they are weary and do not decoy as easily as puddle ducks. Having a scientific collection permit would have allowed us to take birds using non-conventional methods such as from a moving boat. The method of using a fast-moving boat to shoot from has proven successful in another study to collect common mergansers (McCaw et al. 1996) Furthermore, the WDFW did not approve the 10

19 transportation of a shotgun in a state vehicle or the use of a shotgun to collect birds; therefore, we only sampled birds using a conventional hunting license from personal vehicles. Waterfowl counts were conducted between October 2004 and July 2005 to estimate the potential impact of avian predators on the Moses Lake fishery. Literature was used to estimate cumulative consumption rates of common mergansers that were counted on Moses Lake between the apparent bottleneck from October 2004 through March In order to complete this we had to estimate the abundance of common mergansers between the flight counts by determining the area under the line. This method was repeated and checked by fitting a line between the initial number of common mergansers counted at the beginning of October 2004 and the November 2004 monthly surveys. Using the equation of the line we estimated the number of common mergansers that were present during the remaining days surveys were not conducted from November 2004 to March We could only assume there was a linear relationship between each point (survey) to estimate common merganser abundance using both the area under a line and the equation of a line. The estimate for common merganser abundance was used to calculate an average daily consumption rate of 27% body weight using a female population, a male population, and a 1:1 male to female population. A search of historical WDFW waterfowl count data was also conducted to determine if there has been an increase in the number of avian predators as suggested by the local anglers. Because of the lack of the avian predator diet study, we developed a foraging study aimed at determining the foraging success of double-crested cormorants, grebes, and common mergansers. Scan and focal observations (Altmann 1974) were conducted in order to record the number of dives performed by the three target species as well as the subsequent capture of fish associated with a dive. A pilot study suggested that when a fish was observed in the beak of a bird a swallowing motion followed shortly thereafter. Consequently, we developed an ethogram that contained the behaviors diving, fish captured, and swallowing, and assumed that if a fish performed a swallowing motion a fish had indeed been captured. During a bout of observations, we would watch one or two fish for 12 minutes and record behaviors. We also conducted a scan of the 11

20 immediate area every two minutes and recorded the total number of birds that were present. c. Results. i. Fish Predators. During the winter and early spring of , we collected 183 stomach samples from walleye in Moses Lake. As in previous Moses Lake diet studies, yellow perch comprise the highest prey item percentage by weight for both juvenile and adult walleye (Figures 5 and 6). Invertebrates were present within the diets of a number of the walleye but were negligible relative to fishes within the diet. Bioenergetics modeling indicated that yellow perch and black crappie were important prey items of a walleye s diet during February and March (Figure 7). Because we did not have a current abundance estimate, we conducted our bioenergetics modeling on 1,000 walleye based on cohort proportion estimates from the 2004 Fall Walleye Index Netting (FWIN). During the sampling period from February 11, 2005 to March 2, 2005, we estimated that 1,000 walleye consumed over 200,000 grams of fish and exhibited an ontogenetic shift in prey items from zooplankton and invertebrates to fishes, namely yellow perch (Table 2). 12

21 Winter 2005 Juvenile Walleye n = 41 Yellow Perch 82.4% Other Fish spp. 17.6% Figure 5. Diet composition of juvenile walleye captured in Moses Lake, Washington during winter and early spring Winter 2005 Adult Walleye n = 142 Centrarchids 21.9% Yellow Perch 72.8% Rainbow Trout 3.5% Other Fish spp. 1.9% Figure 6. Diet composition of adult walleye captured in Moses Lake, Washington during winter and early spring

22 Proportion day 1 day YP BC RBT Unknown Fish Daphnia Inverts Figure 7. Proportion of fish in the diets of 1,000 walleye during winter and early spring in Moses Lake, Washington based on bioenergetics modeling. Table 2. Grams of prey items consumed by 1,000 walleye from February 11, 2005 to March 2, 2005, in Moses Lake, Washington. Age Black Other Rainbow Yellow Daphnia Invertebrates Crappie Fishes Trout Perch , , , , , , , , , , Total 52, , , , , , ii. Avian Predators. Common mergansers were the most common avian predator on Moses Lake between October 2004 and July 2005 (Figure 8). Gulls (Family Laridae) were second most abundant which can be attributed to 3,500 gulls on Moses Lake during April 2005 (Figures 8 and 9). The irrigation season begins during April, and gulls of various species 14

23 are often seen congregating around the Crab Creek confluence as well as the outlets where they forage on fish that are stunned after passing through the dams. During the winter, gulls, grebes, and double-crested cormorants were virtually absent from Moses Lake (Figures 9, 10, and 11). Conversely, the winter was when common mergansers were most abundant except when ice covered 100% of Moses Lake (Figure 12). Waterfowl counts have been conducted by the WDFW throughout the Columbia Basin during the winter when migratory birds are present. Historical data suggest that there has been an increase in common merganser abundance on Moses Lake during the month of December from (Figure 13). Gulls 37% Common Merganser 50% Common Merganser Cormorant Grebe Gulls Grebe 8% Cormorant 5% Figure 8. Total species composition of avian predators on Moses Lake, Washington between October 2004 and July

24 Gulls Ice Percentage Number % of ice cover Oct 04-Nov 04-Dec 05-Jan 05-Feb 05-Mar 05-Apr 05-May 05-Jun 05-Jul 10 0 Figure 9. Monthly abundance of gull on Moses Lake, Washington between October 2004 and July

25 Grebe Ice Percentage Number % of ice cover Oct 04-Nov 04-Dec 05-Jan 05-Feb 05-Mar 05-Apr 05-May 05-Jun 05-Jul Figure 10. Monthly abundance of grebes on Moses Lake, Washington between October 2004 and July

26 Cormorant Ice Percentage Number % of ice cover Oct 04-Nov 04-Dec 05-Jan 05-Feb 05-Mar 05-Apr 05-May 05-Jun 05-Jul Figure 11. Monthly abundance of double-crested cormorants on Moses Lake, Washington between October 2004 and July

27 Common Merganser Ice Percentage Number % of ice cover Oct 04-Nov 04-Dec 05-Jan 05-Feb 05-Mar 05-Apr 05-May 05-Jun 05-Jul 10 0 Figure 12. Monthly abundance of common mergansers on Moses Lake, Washington between October 2004 and July

28 December 3500 # of Common Mergansers Years Figure 13. Counts of common mergansers on Moses Lake, Washington during the month of December from Individual bird feeding behavior data were collected from double-crested cormorants, common mergansers, and grebes. From February 25, 2005 to May 20, 2005, we conducted 138 behavioral observations equating to 1,058.6 minutes. The majority of data were collected from common mergansers, as they were most abundant during the winter when this task was conducted. Consequently, we observed common mergansers for minutes, double-crested cormorants for minutes, grebes for 199 minutes, and a combination of common mergansers and double-crested cormorants for 24 minutes (Table 3). During the observations, we witnessed diving behaviors 2,508 times. We assumed that this behavior was foraging related as we often recorded fish in the mouths of surfacing birds. Our data suggested that birds were successful at capturing and or swallowing fish on 13.2% of the recorded dives. Common mergansers were the most abundant avian predators from October 2004 to the end of April We calculated daily consumption using data for male and females from the literature (Canadian Council of Ministers of the Environment 1999) and estimated that common mergansers consumed 47,086.7 kg, 65,317.5 kg, and 56,221.2 kg of prey items for all female and male populations and a population consisting of 1:1 males and females, respectively. 20

29 Table 3. Summary of avian piscivorous foraging behaviors on Moses Lake, Washington from February 2005 through May Species Dive Fish Swallow % Ingested Min Double-crested cormorant Common merganser 2, Grebe Common merganser/double-crested cormorant 24 d. Discussion. It appears that the combination of avian and piscivorous predators utilizing Moses Lake impacts the resident fish population. Since the 1980s, the abundance of both groups of predators has increased considerably (Bennett et al. 2002, WDFW 2004). Results from our completion report suggested that the impact of walleye on the fishes of Moses Lake was tremendous (Burgess et al. 2007) and suggested an over-winter bottleneck. Consequently, the purpose of this task was to develop a better understanding of the factors that impact the Moses Lake fishery during the winter. Moses Lake can hold a large number of waterfowl throughout the year, many of which are piscivorous. Furthermore, continuous waterfowl counts and nesting counts suggest an upward trend in common merganser and double-crested cormorant abundance (WDFW 2004). Before the USBOR Columbia Basin Irrigation Project, little lacustrine water was located within the Columbia Basin. After the construction of the Potholes Channel in 1955 and the ensuing flooding of desert areas, considerably more watered habitat was created (USBOR 1998). South of Moses Lake, in the Potholes Reservoir, the numbers of breeding double-crested cormorants went from 16 pairs in 1978 to 652 breeding pairs in 1997 (Finger and Tabor 1997). The altered habitat is ideal for migrating waterfowl including avian predators and the increase in abundance is reflected in WDFW winter waterfowl counts (WDFW 2004), and in the literature (Carter et al. 1995; Roby et al. 1998). Local studies have found that common mergansers and double-crested cormorants feed on salmonid fishes (Wood 1987) and they can impact native salmonids 21

30 (Roby et al. 1998, Stephenson 2003) as well as stocked trout (Major 1999). Nationally and internationally, a considerable amount of attention is directed towards double-crested cormorants, as they are believed to be responsible for negatively impacting resident fisheries and aquaculture practices (Carss et al. 1997; Wires et al. 2001). Regionally, the three most abundant avian predators on Moses Lake were common mergansers, doublecrested cormorants, and various grebe species. However, the utilization of Moses Lake by avian predators during the winter is our primary concern as winter was identified as a bottleneck with respect to young fish survival. In conclusion, monthly counts suggest substantial numbers of fish eating birds that inhabit Moses Lake during various times of the year. As well as impacting the Moses Lake fishery, the same predatory birds may also be affecting ESA listed fishes within the Mainstem Columbia River as some evidence suggests many migrate laterally between the bodies of water within the Columbia Basin. Common mergansers have been found to be the most abundant avian predator within the Yakima Basin during spring and summer (Stephenson 2003) but are virtually absent on Moses Lake during the same time. However, during the late fall and winter, common mergansers become very abundant on Moses Lake and less so within salmonid bearing waters. For example, in December 2004 when 2,280 common mergansers were counted on Moses Lake, only 131 common mergansers were counted on the pools at the combined locations of Wanapum, Rock Island, Rocky Reach and Wells dams on the Columbia River (WDFW 2004). It is quite possible that avian predators may utilize many of the inland lakes and reservoirs including Moses Lake as a resource refuge during the winter and breed and feed in salmon bearing waters during the spring and summer when they are know to impact native salmonids (Roby et al. 1998, Stephenson 2003). In doing so, avian predators may have increased fitness as increase in waters containing fishes within the basin has negated the need to migrate long distances in search of food. The impacts of avian predators although potentially large are relatively insignificant compared to the impacts of walleye on the Moses Lake fishery. Our analysis suggests that even though the temperatures are far below the optimal growth range (Koenst and Smith 1976; Hokanson 1977) the consumption of prey fish by walleye is still elevated. 22

31 As well as the impact of avian and piscivorous predators on Moses Lake fishery, managers should also examine the impact to connected systems, including the mainstem Columbia River. The lateral migration of avian predators, and the entrainment of nonnative deleterious fish species to areas where sensitive species exist could hamper restoration and recovery efforts of native salmonids. With respect to the fishery in Moses Lake, the overabundance of both avian and fish predators will continue to limit additional desirable game fish production. For most of the year, the walleye fishery is not accessible by many anglers as it is such a specialized fishery, unlike a panfish fishery. Ideally, we would like to see Moses Lake re-establish a generalized fishery by decreasing the abundance of walleye while still maintaining a walleye fishery. B. Objective 2. Refine management direction based on current information from Phase I investigations. Task Application of modeling technology to augment understanding of the Moses Lake fishery. Task Carp isolation and removal. 1. Task Application of modeling technology to augment understanding of the Moses Lake fishery. a. Introduction. Application of Phase I results enables us to quantitatively exercise changes in mortality on fish community structure in Moses Lake. Phase I results suggest that fish predation has a huge effect on the population structure of the target species in Moses Lake. Enhanced predator abundance populations can severely reduce recruitment of prey populations. Thus, overabundance of predators can sufficiently reduce recruitment of selected target species and conversely, reduced predator abundance can increase recruitment. Modeling can effectively simulate the Moses Lake ecosystem dynamics and predict outcomes of management decisions. Population models, such as FAST (e.g. Fisheries Analysis and Simulation Tools), were applied to the Moses Lake ecosystem to assess effects of mortality changes (Slipke 23

32 and Maceina 2001). FAST enhances understanding of the dynamics of fish populations and the influence of changes in mortality on long-term population structure. b. Methods. Data from the FWIN surveys were applied to the FAST model to forecast population and cohort behaviors using the dynamic pool and yield per recruit models, respectively. Before using the FAST model, several parameters had to be estimated, specifically growth and mortality. Growth was determined using the Von Bertalanffy growth equation: L t = L k ( t-to) [ 1 e ] Where: L = Maximum theoretical length, k = Growth coefficient, t = Time or age in years, to = Time when length would be equal to 0, and e = Exponent for natural logarithms. The Von Bertalanffy computation is one that can be calculated using the FAST model and was done by inputting the mean length of aged fish. During the annual FWIN surveys, we collected otoliths from all captured walleye and sent the samples to the WDFW aging lab in Olympia, Washington for analysis. For the FAST model, it was also necessary to determine the relationship between length and weight using the following regression formula: W = al b. Or, the simpler equation: log 10 (W) = log 10 a+b * log 10 (L), where: W = weight (g), 24

33 L = length (mm), a = intercept, and b = slope. a and b are coefficients that vary among species, habits etc. Total mortality, mortality associated with fishing, and natural mortality were estimated and entered into the model. Although the FAST model is capable of calculating mortality, we elected to use our mortality calculations that we have used for the bioenergetics modeling. To estimate annual mortality, we first determined annual survival using the Chapman-Robson estimator (Everhart and Youngs 1981): T Ŝ = n + T -1 where: Ŝ = annual survival, T = k x = 0 xf x = the sum of the coded age times its frequency, x = the coded ages, f x = the frequencies, and n = k f x x = 0 = the sum of the frequencies. Finally, assuming annual survival is the compliment of annual mortality, we calculated mortality using: A = 1 S where: A = annual mortality. 25

34 Once we calculated annual mortality and annual survival, we then calculated the instantaneous annual rate of total mortality (Z) by taking the negative natural log (ln) of survival (S). Z = -ln (S). Finally, we proportioned the mortality to either conditional fishing (cf) or conditional natural mortality (cm). c. Results and Discussion. At the current exploitation rate of 1.22%, the model output suggests that there will be no impact on the walleye population by recreational anglers. This is corroborated by our results and data from previous creel surveys indicating that walleye are an underutilized resource and clearly may be negatively impacting other desired fishes. In light of consumption rate analysis, a population estimate, and our creel survey we concluded that the walleye fishing regulation should be changed in order to increase exploitation and decrease walleye abundance. We have recommended the regulations be changed from a regulation of five walleye, 18 in or larger with one over 24 in to a regulation of eight walleye 12 in or larger with one over 24 in. We do not expect to see an increase in the number of fish 18 in or larger that are harvested but an obvious increase in the number of smaller walleye harvested. In the past, the largest numbers of anglers fishing on Moses Lake are those that are fishing for any species. Consequently, we expect these anglers to comprise the majority of anglers that harvest smaller walleye. 2. Task Carp isolation and removal. a. Introduction. Literature suggests carp can negatively impact the aquatic ecosystems they inhabit (Tyus and Saunders 2000; Parkos et al. 2003). Results of Phase I suggested that the most detrimental impacts to juvenile gamefish occurred during the winter. Our findings in 26

35 Phase I also suggested that secondary productivity in Moses Lake was not limiting fish production, although possible interactions among fishes may be a limiting factor of recruitment of target fishes. However, carp are an undesirable fish and there is great pressure to address the carp issue within Moses Lake. With this in mind, a black crappie rearing sanctuary was created in an isolated portion of the lake previously identified as a large-scale carp spawning site. The result has been increased black crappie production in the rearing area and apparent, although not quantified, improved recruitment throughout the lake. Other less conventional carp removal has previously been employed on Moses Lake. For example, a bow-fishing tournament in 2003 removed over 16,000 lbs of carp in 2 days. Increased mortality and exclusion of carp from the most productive spawning areas could potentially enhance target fish survival and abundance. b. Methods. Using previously collected carp abundance data and anecdotal information, and identifying areas that are morphologically suitable for targeting carp, we developed a carp removal strategy. The efforts for carp removal were broken down into two categories: promoting carp removal events and constructing carp exclusion areas. i. Carp Exclusion Areas. The purpose of a carp exclusion area is either to keep carp out of a particular area or allow them to enter an area where they would be trapped and removed. Several criteria had to be met to be considered a potential area of carp exclusion. 1. High probability of carp utilization. 2. A cove or bay with a narrow opening to facilitate easy construction and maintenance of carp barrier. 3. No interference with public use (e.g. vessel movement). ii. Promoting Carp Removal Events. 27

36 Pacific Northwest Bowfishing currently organizes a successful carp bowfishing tournament that takes place each June. Rather than attempting to start an additional tournament, we will work with the sponsors to promote the current event. The WDFW has an extensive media network and the ability to reach a large base of people that may be interested in such an event and ultimately increase the total harvest of carp. c. Results and Discussion. We designated two coves in Section 3 and one in Section 2 as ideal locations to install carp exclusion barriers (Figure 14). Carp exclusion zones will be constructed similarly to the structure developed by the MLID, which was developed at the northern outlet of Pelican Horn in Section 1, and has removable gates with two-inch gaps across the entire face of the structure (Figure 15). Although no baseline data regarding carp abundance were collected before the construction of the MLID carp barrier, WDFW District 17 Biologist Jeff Korth has noticed a marked decrease in carp numbers. Before deploying similar carp barriers in our predetermined locations, we will conduct an abundance estimate as well as determine species composition as a measure of baseline data, which will be used to gauge the effectiveness of our barriers. 28

37 Figure 14. Areas encompassed by an oval have been identified as ideal locations to install carp exclusion barriers in Moses Lake, Washington. 29

38 Figure 15. Carp exclusion barrier on Moses Lake, Washington constructed by the Moses Lake Irrigation district. III. Conclusion. This year s work was a continuation of previous tasks and addressed unknown limiting factors on Moses Lake. An initial year of analyses suggested that entrainment and piscivory are major sources of mortality for prey fishes in Moses Lake, which was corroborated by this year s analysis. This year s bioenergetics modeling filled in a much needed gap, because we previously lacked an adequate winter consumption estimate. The angling community has long thought that the avian component, specifically double crested cormorants has been responsible for the fluctuations in the Moses Lake Fishery. The impact of avian predators has been documented on other systems but not confirmed on Moses Lake until this year. Using consumption estimates from the literature and our monthly waterfowl counts we were able to suggest that avian predators on Moses Lake did consume a considerable number of fishes. Due to the limited scope of the data collections as a result of several state and federal permitting issues we were not able to collect specimens to determine what species were most being impacted by the fish eating birds. 30

39 The combined impacts of predation (avian and fish) and entrainment negatively affect the fishery of Moses Lake. In order to lessen the impact of piscivorous predators, we have suggested to the WDFW managers that the bag limit on walleye be changed to reduce the abundance of smaller walleye while preserving the quality walleye fishery within Moses Lake. The proposed limit is 8 fish, 12 minimum with one over 24. Once this regulation change is implemented, it will be important to monitor the fish community in order to detect whether or not a response is elicited. An important component of the Moses Lake fishery that must be collected is a creel survey to determine if there is an anthropogenic response as a result of the new regulation. In conclusion, previous data and analysis will allow us to focus our efforts on winter predation and entrainment as well as walleye production. We will also recommend that the WDFW conduct a creel survey using the methodologies we previously developed in order to have a comparable study. In the future we will propose an additional more comprehensive avian predation study in order to not only determine the impact of avian predators on Moses Lake but the possible connection between resident and anadromous fishes as a result of temporal lateral migrations between waters. 31

40 IV. Literature Cited. Altmann, J Observational study of behavior: sampling methods. Behaviour 49(3): Bennett, D. H., J. W. Korth, and D. S. Burgess Factors Affecting the Recreational Fishery in Moses Lake, Washington. Project ID: NWPPC approved project proposal. Burgess, D. S., K. E. Simmons, and D. H. Bennett Factors Affecting the Recreational Fishery in Moses Lake, Washington. Project ID: BPA Completion Report. Canadian Council of Ministers of the Environment Protocol for the Derivation of the Canadian Tissue Residue Guidelines for the Protection of Wildlife that Consumes Aquatic Biota. 18 pp. Carter, H. R., A. L. Sowls, M. S. Rodway, U. W. Wilson, R. W. Lowe, G. J. McChesney, F. Gress, and D. W. Anderson Population Size, trends, and conservation problems of the double-crested cormorant on the Pacific Coast of North America. Colonial Waterbirds, Special Publication 1: The Double-Crested Cormorant: Biology, Conservation and Management 18: Carss, D. N. and The Diet Assessment and Food Intake Working Group Techniques for assessing cormorant diet and food intake: towards a consensus view. Supplementi Ricerche Biologia Selvaggina 26: Evans, C. and A. Larson Moses Lake Inflow-Outflow Balance - A Component of the Moses Lake Total Phosphorous Total Maximum Daily Load. Washington Department of Ecology Report. Publication Number Everhart, W. H. and W. D. Youngs Principles of Fishery Science. 2 nd Edition. Comstock Publishing Associates, a division of Cornell University Press. Ithaca, NY. 349 pp. Finger, S. and J. Tabor Inventory of colonial nesting birds on Potholes Reservoir. Washington Department of Fish and Wildlife. Unpublished report. Glahn, J. F. and K. E. Brugger The impact of double-crested cormorants on the Mississippi Delta catfish industry: a bioenergetics model. Colonial Waterbirds, 32

41 Special Publication 1: The Double-Crested Cormorant: Biology, Conservation and Management 18: Hansel, H. C., S. D. Duke, P. T. Lofy, and G. A. Gray Use of diagnostic bones to identify and estimate original lengths of ingested prey fishes. Transactions of the American Fisheries Society 117: Hokanson, K. E. F Temperature requirements of some percids and adaptations to the seasonal temperature cycle. Journal of the Fisheries Research Board of Canada 34: Koenst, W. M. and L. L. Smith Jr Thermal requirements of the early life history stages of walleye, Stizostedion vitreum, and sauger, Stizostedion canadense. Journal of the Fisheries Research Board of Canada 33: Major, W. III Double-Crested Cormorant (Phalacrocorax auritus) abundance and foraging behavior in response to three rainbow trout stocking strategies at Central Washington State lakes. Master Thesis Report. WSU Dept. of Natural Resource Sciences. Major, W. III, C. C. Grue, K. Ryding, and J. M. Grassley Development of an index to bird predation of juvenile salmonids within the Yakima River. Project No BPA Report DOE/BP McCaw J.H., P.J. Zwank, and R.L. Steiner Abundance, distribution and behavior of common mergansers wintering on a reservoir in Southern New Mexico. Journal of Field Ornithology. 67(4): Merritt, R. W. and K. W. Cummins An Introduction to the Aquatic Insects of North America. 3 rd Edition. Kendall/Hunt Publishing Co. Dubuqe, IA. 862 pp. Parkos, J. J. III, V. J. Santucci Jr., and D. H. Wahl Effects of adult common carp (Cyprinus carpio) on multiple trophic levels in shallow mesocosms. Canadian Journal of Fisheries and Aquatic Sciences 60(2): Pennak, R. W Fresh-Water Invertebrates of the United States: Protozoa to Mollusca. 3 rd Edition. John Wiley and Sons Inc. New York, NY. 628 pp. Roby, D. D., D. P. Craig, K. Collis, and S. L. Adamany Avian predation on juvenile salmonids in the lower Columbia River. Annual Report for BPA, Portland Oregon. 33

42 Scheaffer, R. L., W. Mendenhall, and L. Ott Elementary Survey Sampling. 5 th Edition. Duxbury Press, Boston, MA. Schramm, H. L. Jr., M. W. Collopy, and E. A. Okrah Potential problems of bird predation for fish culture in Florida. The Progressive Fish-Culturist 49: Slipke, J. W. and M. J. Maceina Fishery Analyses and Simulation Tools (Fast 2.0). Department of Fisheries and Allied Aquacultures Auburn University. Stephenson, A. E Development of an index to bird predation of juvenile salmonids within Yakima River Annual Report US Department of Energy, Bonneville Power Administration. Stewart, D. J., J. F. Kitchell, and L. B. Crowder Forage fishes and their salmonid predators in Lake Michigan. Transactions of the American Fisheries Society 110: Tyus, H.M. and J.F. Saunders III Nonnative fish control and endangered fish recovery: lessons from the Colorado River. Fisheries 25: USBOR USBOR History of Columbia Basin Irrigation project. WDFW Region 2 Wildlife Program. Unpublished monthly waterfowl counts. Winchell, F., S. Amaral, and D. Dixon Hydroelectric turbine entrainment and survival database: an alternative to field studies. Completion Report. Electrical Power Research Institute. Wires, L. R., F. J. Cuthbert, D. R. Trexel, and A. R. Joshi Status of the double crested cormorant (Phalacrocorax auritus) in North America. Final Report to the USFWS. Wood, C.C Predation of juvenile Pacific salmon by the common merganser (Mergus merganser) on eastern Vancouver Island. 1: Predation during the seaward migration. Canadian Journal of Fisheries and Aquatic Sciences 44(5): Wydoski, R. S. and R. R. Whitney Inland Fishes of Washington. 2 nd edition: revised and expanded. University of Washington Press. Seattle, WA. 322 pp. 34