Lake Wanapitei Fall Walleye Index Netting, 2004

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1 Lake Wanapitei Fall Walleye Index Netting, 2004 Kimberley Carmichael, Fisheries Biologist August Wallace Road, Unit 5 North Bay, ON P1B 8G4 Phone: (705) Fax: (705) aofrc@aofrc.org Report A/OFRC 05-04

2 ii S u m m a r y A Fall Walleye Index Netting (FWIN) project was conducted for the first time on Lake Wanapitei in Forty nine net sets were completed across the entire lake. A total of 205 walleye, 31 lake trout, 52 smallmouth bass, and 13 lake whitefish were among the fish captured. Based upon the results of this project, it appears that the Lake Wanapitei walleye population is in a stressed condition. Abundance is low and the population is dominated by young, fast growing and early maturing fish. More knowledge on the current harvest is required to determine if the fishery is sustainable or not. The implementation of a subsistence catch sampling program would provide both First Nations and Ontario Ministry of Natural Resource managers with additional information regarding the harvested population. Fall Walleye Index Netting studies should be used in order to track further changes in walleye population dynamics.

3 iii A c k n o w l e d g e m e n t s We would like to acknowledge the efforts of Larry McGregor, Wally McGregor and Maureen Peltier who worked tirelessly on completing the fieldwork for this project. We are indebted to George Morgan and Michael Malette of the Freshwater Ecology Unit who aided in data synthesis.

4 iv T a b l e o f C o n t e n t s Summary... ii Acknowledgements... iii List of Tables... v List of Figures... v Introduction... 1 Methods... 3 Results... 4 Discussion... 8 References Appendix 1. Total Criteria Table as written in Morgan et al (2005 presentation)... 15

5 v L i s t o f F i g u r e s Figure 1. Region Surrounding Lake Wanapitei (Greater City of Sudbury 2005)... 1 Figure 2. Contour Map of Lake Wanapitei (Greater City of Sudbury 2005)... 2 Figure 3. Lake Wanapitei 2004 FWIN Netting Sample Sites and Contaminant Sample Sites... 4 Figure 4. Weight (g) Distribution of Wanapitei Walleye Population... 6 Figure 5. Total Length (mm) Distribution of Lake Wanapitei Walleye... 6 Figure 6. Age Structure (years) of Lake Wanapitei Walleye Population... 7 Figure 7. Maturity Rates for Male and Female Walleye... 7 Figure 8. Walleye Distribution over Lake Wanapitei Figure 9. Figure 10. Figure 11. Growth Rate Comparisons for Male and Female Walleye; Lake Wanapitei vs. Northeastern Ontario Average Condition Equation Determined by the Compendium Printout (Kushneriuk and Lester 1996) Log Weight- at Log total Length for Male and Female Walleye in Lake Wanapitei and the Northeast Region Benchmarks L i s t o f T a b l e s Table 1. FWIN Catch Data by Species (all strata combined), Lake Wanapitei Table 2. Table 3. Mean Walleye Age, Weight and Total Length for Female, Male and Combined Sexes... 5 Average Biological Characteristics of Northeast Walleye and Lake Wanapitei (OMNR 2003)... 9 Table 4. Lake Comparisons for Different Characteristics of FWIN Table 5. Walleye Benchmark Classifications for FWIN Projects (Morgan 2005) Table 6. Walleye Benchmark Classification for Lake Wanapitei 2004 FWIN... 12

6 1 I n t r o d u c t i o n Lake Wanapitei was formed 37.2 million years ago, when the impact of a meteorite created a crater that was shaped like a tooth. The First Nation ties to the land date back to the woodland period of the seventeenth centry, so its suiting that Lake Wanapitei s name comes from the Ojibwa word Wahnabitaybing, or "tooth" (City of Sudbury 2005). Lake Wanapitei is located northeast of Sudbury (Figure 1). It is one of the largest inland lakes in the province with a surface area of ha (OMNR 2005). It is also a very deep lake with a maximum depth of m located at the southwestern end of the lake (Figure 2). The southwestern shoreline is developed with cottages and homes. Wanapitei has 370 permanent residents and 180 seasonal/recreational residents (Greater Sudbury 2005). Figure 1. Region Surrounding Lake Wanapitei (Greater City of Sudbury 2005) The Wahnapitae First Nation is located on the north shore of Lake Wanapitei, approximately 29 kilometers northeast of Sudbury, Ontario, and has a total membership of 326, with an on-reserve population of 36 (as of June 2003) (Indian and Northern Affairs 2005). There are multiple

2 stakeholders with an interest in the lake including the First Nation, mining companies, resorts and other concerned residents from surrounding communities such as Skead. Figure 2.

7 2 stakeholders with an interest in the lake including the First Nation, mining companies, resorts and other concerned residents from surrounding communities such as Skead. Figure 2. Contour Map of Lake Wanapitei (Greater City of Sudbury 2005) This deep cold water lake supports a variety of fish species. Walleye, pike and smallmouth bass make up the near shore community; lake trout, herring and lake whitefish comprise the pelagic fish community. Lake trout and northern pike are native to Lake Wanapitei. It is believed that walleye were first introduced around Braggs et al (1962) believe the walleye were introduced via high water levels from Lake Matagamasi. The same mechanism is thought to have introduced the smallmouth bass in Lake herring were introduced by the OMNR in 1951 as an additional food source for lake trout (Braggs et al 1962). All other species, such as, burbot, lake whitefish, rock bass, pumkinseed, yellow perch, and white sucker are native to Lake Wanapitei. Lake Wanapitei provides year round recreational angling opportunities, where mainly lake trout and walleye are sought after. There is a history of commercial fishing on Lake Wanapitei. Presently one non-aboriginal fisherman has a commercial fishing license (Keith Scott 2005) who targets whitefish and common white sucker. Lake Wanapitei supports a modest subsistence fishery for the Wahnapitae First Nation. There has been a lot of concern surrounding the Ontario Power Generation Inc. (OPG) dam that regulates the level of Lake Wanapitei. The mean annual fluctuation is 8 feet with extremes of 4 feet to 11 feet (Braggs et al 1962). There have also been concerns on the impact of the neighboring mining activities on the lake watershed. The Wahnapitae First Nation is working with FNX mining and Golder Environmental Limited on water quality monitoring on Post Creek which runs into Lake Wanapitei.

8 3 A walleye population assessment has never been completed on the lake prior to this project. The last fisheries study conducted by the OMNR on Lake Wanapitei was lake whitefish sampling in 1960, 1961, and The A/OFRC decided a Fall Walleye Index Netting (FWIN) survey would address some of the Lake Wanapitei First Nation concerns and form a baseline for future fisheries management plans for Lake Wanapitei. The purpose of this report is to evaluate the present stock status of the Lake Wanapitei walleye population. M e t h o d s The project followed the methodology outlined in the FWIN Manual of Instructions (Morgan 2002). The FWIN survey is a standardized protocol that involves setting gillnets with 8 different mesh sizes ranging from 25mm 152 mm. In order to sample both young/small and old/large walleye three nets were set each night for a 24 hour period. A total of 49 nets were set at random locations throughout Lake Wanapitei (Figure 3). The lake was stratified into two depths, 2-5m and 5-15m. Because of the lake size the minimum amount of sets required was 48 (Morgan 2002). The FWIN is a gillnetting method that lethally samples the walleye population. All sport fish were biologically sampled [total length, fork length, weight, ageing structures (otoliths and scales), stomach contents, sex, and gonad condition]. Flesh samples were collected for contaminant analysis from the walleye (Figure 3). All other fish species were counted and length tallied. This assessment technique provides important information to assess the walleye stock status. The biological attributes measured by the FWIN include, relative abundance of adults and juveniles, age structure, growth, condition, sex and maturity, fecundity, recruitment, community structure and contaminant analysis (Morgan 1998). All catch and morphometric data were entered into the software package FISHNET (V 2.0). Age interpretation was carried out by a qualified technician, Bob Irwin. Statistical analyses were conducted using SYSTAT 10.2 for Windows (SYSTAT 2002).

4 Figure 3. Lake Wanapitei 2004 FWIN Netting Sample Sites and Contaminant Sample Sites R e s u l t s Netting commenced on September 21/04 and concluded on October 06/04.

9 4 Figure 3. Lake Wanapitei 2004 FWIN Netting Sample Sites and Contaminant Sample Sites R e s u l t s Netting commenced on September 21/04 and concluded on October 06/04. Surface water temperatures ranged from degrees Celsius and a total of 49 net sets were completed (Figure 3). Walleye, lake herring, and smallmouth bass made up the largest proportions of the total catch (Table 1). The catch per unit effort (CUE) for walleye was 4.18 walleye per net (Table 1).

10 5 Table 1. FWIN Catch Data by Species (all strata combined), Lake Wanapitei 2004 Species Total Captured (n) Percent of Total Catch C.U.E (no/net) % RSE Lake Trout Lake Whitefish Lake Herring Rainbow Smelt Northern Pike White Sucker Lake Chub Burbot Rock Bass Small mouth Bass Yellow Perch Walleye The mean age indicate that the population consists of young walleye (Table 2). 65 % of all captured walleye weighed less than 500g (1lb) (Figure 4). The proportion of total length in the walleye population peaks around 330mm (Figure 5). Female walleye are approximately 502 mm in length when they are 50% mature while males are 409 mm. Table 2. Mean Walleye Age, Weight and Total Length for Female, Male and Combined Sexes. Walleye Sex Mean age (yrs) Mean weight (g) Mean total length (mm) Female Male Combined The population consists of young walleye (Figure 6). The age frequency for walleye captured indicates a strong 2002 year class (2 year olds) and a relatively strong 1999 year class (5 year olds) (Figure 6). The maturity schedules indicate that males are 50% mature at approximately 3 years of age and females are 50% mature at age 3.5 (Figure 7). The sex ratio of mature males to mature females is estimated to be 48/13 = The sex ratio of mature/immature for males is 48/36 = 1.33 and for females 13/44 = Robson and Chapman (Ricker 1975) gave a mortality rate after 5 yrs of age of 69% for males and 53% for females. Mortality rates for walleye greater than age 3 are 33% for females and 39% for males.

11 Proportion of walleye Proportion of Walleye Weight (g) Figure 4. Weight (g) Distribution of Wanapitei Walleye Population Figure Total Length (mm) Total Length (mm) Distribution of Lake Wanapitei Walleye.

12 Proportion walleye pop Age (years) Figure 6. Age Structure (years) of Lake Wanapitei Walleye Population Proportion Mature Age (years) MALE FEMALE Figure 7. Maturity Rates for Male and Female Walleye.

8 D i s c u s s i o n Given the size of Lake Wanapitei, 49 net sets were done to achieve an acceptable level of precision (i.e. relative standard error <20 percent).

13 8 D i s c u s s i o n Given the size of Lake Wanapitei, 49 net sets were done to achieve an acceptable level of precision (i.e. relative standard error <20 percent). However the required precision level was not attained (RSE of 25 percent) likely as a result of patchy distribution. Walleye catches were lower in the southern deeper portion of the lake. Walleye capture rate, catch per unit effort (CUE) values, from FWIN surveys are proportional to walleye density. Therefore CUE is the first and key diagnostic variable. The bottom 25% of the provincial data represents low catches (less than 5 walleye per net) and top 25% high catches (greater than 15 walleye per net) (MNR 1998). The CUE for Lake Wanapitei is low, with a value of 4.18 walleye per net. Physical parameters such as; lake size, community, total dissolved solids (TDS), and habitat suitability affects walleye catches. It is important to differentiate between the natural state of the population (determined by lake characteristics and fish community), and stress acting upon the population. Habitat may play a role in the distribution of the walleye in Lake Wanapitei. The habitat in the southern end is deeper and more suited for lake trout; where as, habitat in the north end consists of shallower sandy bars that are more suited for walleye (Figure 8). Figure 8. Walleye Distribution over Lake Wanapitei 2004

14 9 Walleye population dynamics suggest that this population is composed of young walleye; 1, 2 and 3 year olds (Figure 6). When comparing Wanapitei population parameters to the Northeastern regional average of Ontario (Table 3) the main differences are; a lower relative abundance of 4.18 walleye/net, females mature at a greater size and at an earlier age and they are faster growing. Table 3. Average Biological Characteristics of Northeast Walleye and Lake Wanapitei (OMNR 2003) Population Characteristic Northeast Region Average Lake Wanapitei Relative Abundance 6.4 walleye/net 4.18 walleye/net Total Length (mm) Weight (g) Female Mortality 29% 33% Male Mortality 31% 39% Female Max. Size 75.5 cm 75.0 cm Male Max. Size 63.1 cm 65.0 cm Female size-at-maturity 44.1 cm 50.2 cm Male size-at-50%maturity 34.9 cm 40.9 cm Female age-at-50%maturity 4.5 yrs 3.5 yrs Male age-at-maturity 2.9 yrs 3.0 yrs The Von Bertalanffy equation, L(t) = L (1 - exp[-k(t-to)]), describes the rate of growth for Lake Wanapitei walleye to be: female L t = 826 (1- e (t) ) and males L t = 628 (1- e (t) ). The growth rate modeled for the walleye in Lake Wanapitei is much more rapid than the Northeastern benchmarks (Figure 9) (OMNR 2003). Growth can be a useful indicator of population status because it responds quickly to changes in population density. Rate of growth would be expected to increase with increasing exploitation; however this relationship may be confounded by food availability.

15 Total Length (mm) Wanapitei Females Wanapitei Male NE Females NE Males Age (years) Figure 9. Growth Rate Comparisons for Male and Female Walleye; Lake Wanapitei vs. Northeastern Ontario Average. Lake Wanapitei walleye condition can be expressed using the equation W=aL b (Figure 10). Figure 11 illustrates the similarity in condition between Lake Wanpaitei and the Northeastern regional benchmarks. Condition can be an indicator of food availability but it does change depending on the inherent shape of individual fish and species. Figure 10. Condition Equation Determined by the Compendium Printout (Kushneriuk and Lester 1996)

16 Log Weight (g) Male Female NE female NE male Figure Log Total Length (mm) Log Weight- at Log Total Length for Male and Female Walleye in Lake Wanapitei and the Northeast Region Benchmarks. When Lake Wanapitei is compared to other lakes of similar size, latitude, and productivity, the mean lengths (mm) are similar; where as the mean weight of Wanapitei is slightly higher. Walleye mortality is higher in Lake Wanapitei relative to these other lakes and abundance is moderate (Table 4). Table 4. Lake Comparisons for Different Characteristics of FWIN Characteristics Lake Temagami Lac Kipawa Lake Onaping Lake Wanapitei (2001) (1996) (2000) (2004) Size (ha) 20, ,044 6,868 18,837 Secchi Mean Depth (m) GDD> Mean Length (mm) Mean Weight (g) Mean Age (years) CPUE (no walleye/net) Mortality(female age 5 onwards)

12 Morgan (2005) determined how to separate healthy, stressed, and unhealthy walleye populations by looking at key FWIN characteristics and life history characteristics (Appendix 1).

17 12 Morgan (2005) determined how to separate healthy, stressed, and unhealthy walleye populations by looking at key FWIN characteristics and life history characteristics (Appendix 1). He described the basic walleye benchmarks as shown in Table 5. Table 5. Walleye Benchmark Classifications for FWIN Projects (Morgan 2005) Parameter Healthy/Stable Stressed/Unstable Unhealthy/Collapsed CPUE 450mm 2.0 /net /net 0.43/net Number of age classes 11 age classes 6 to 10 age classes 5 age classes Maximum age 16 years years 13 years Shannon diversity index Scoring FWIN data for each parameter in the Walleye Benchmark Classification key; Score AbundanceScore Age Class Score Maximum Age Score 4 ShannonIndex Score Range Unhealthy/Collapsed = 1.0 to Stressed/Unstable = 2 to Healthy/Stable = 3.0 by 0.25 increments (9 classification levels) Following this classification system Lake Wanapitei falls between Stressed/Unstable and Unhealthy/Collapsed (Table 6). Table 6. Walleye Benchmark Classification for Lake Wanapitei 2004 FWIN Parameter Raw Value Score CPUE 450mm Number of age classes 9 2 Maximum age 12 1 Shannon diversity index Maximum sustainable yield (MSY) is a theoretical value of fish harvest which can occur safely, without leading to a collapse in fish stocks to the point where future production is compromised. Fisheries scientists have realized that this definition is not completely accurate, as using MSY as a target level for harvest can make fish stocks vulnerable to over fishing and collapse (Lester et al 2002). MSY estimates are better used as limit reference points, defining thresholds which should never be exceeded. MSY for walleye in Lake Wanapitei was determined as being 0.39 kg/ha a year using the formula found in Lester et al (2002). The following values were used; total dissolved solids (TDS) of mg/l, average depth of 38.3 m, maximum depth of m, secchi of 6.2 m and GDD > 5 C, 1496 (Cobb 2006).

18 13 To get a complete insight to the status of the fishery we require a better understanding of the amount of fish angled over the year and the amount of fish taken by the existing commercial fishery. The implementation of a subsistence and commercial catch sampling program would provide both First Nations and OMNR managers with additional information regarding harvested populations. Monitoring of recreational fishing is also required to gain an idea of total harvest per year. C o n c l u s i o n Results from the 2004 FWIN suggest that the walleye abundance in Lake Wanapitei is below average, relative to other lakes in Ontario. The population is made up of 10 year classes and a large proportion of the population consists of fast growing young fish. The mean age and size of the walleye are low and they mature at a young age. The Lake Wanapitei walleye population is on the boarder of Stressed/Unstable and Unhealthy/Collapsed. Regardless of what the current harvest is, we recommend that harvests be decreased over the next five years in order to allow the population to rebuild. An additional Fall Walleye Index Netting project should be completed in 2009 in order to reassess population status.

19 14 R e f e r e n c e s Braggs, E., C. Edwards, and D. Gillespie A progress report on the lake Wanapitei. OMNR Sudbury District. Cobb, E Ontario Ministry of Natural Resources. Personal Communication. February 16, Greater City of Sudbury Lake water quality: Wanapitei Lake Indian and Northern Affairs Canada Kushneriuk. R. and N. Lester Compendium Printout. Ontario Ministry of Natural Resources. Printed by the Cooperative Freshwater Ecology Unit, Laurentian University, Sudbury Ontario 04/08/05. Lester, N.P., P.A. Ryan, R.S. Kushneriuk, A.J. Dextrase and M.A. Rawson The effect of water clarity on walleye (Stizostedion vitreum vitreum) habitat and yield. Percid Community Synthesis, Ontario Ministry of Natural Resources, Peterborough, Ontario Morgan G.E Fisheries Synthesis Workshops. Percid Synthesis Training Session Sampling standards and diagnostics working group. Manual of Instruction Fall Walleye Index Netting (FWIN). Cooperative Freshwater Ecology Unit, Laurentian University, Sudbury Ontario. Morgan G.E Presentation on walleye benchmark classifications for FWIN projects. Cooperative Freshwater Ecology Unit, Laurentian University, Sudbury Ontario. Ontario Ministry of Natural Resources (OMNR) Percid Synthesis Training Session Sampling standards and diagnostics working group. Fisheries Synthesis Workshop. Ontario Ministry of Natural Resources (OMNR) Regional Summaries of Walleye Life Characteristics Based on Ontario s Fall Walleye Index Netting (FWIN) Program 1993 to Diagnostics and Sampling Standards Working Group Percid Community Synthesis February Ontario Ministry of Natural Resources (OMNR). February Crown Land Use Policy Atlas Policy Report Lake Wanapitei. Pg 1-4 Ricker, W.E Computation and Interpretation of biological statistics of fish populations. Fisheries Research Board of Canada. Bulletin 191, Ottawa. Scott, K Fish and Wildlife Technical Specialist. Ontario Ministry of Natural Resources. Personal Communication. September 13, SYSTAT 10.2 Software for windows SYSTAT Software Inc.

20 15 Appendix 1. Total Criteria Table as Written in Morgan (2005 Presentation) Criteria Indicator Healthy Stressed Unhealthy Catch Mean age 4.6 yrs 3.8 yrs 4.0 yrs Maximum age 17.4 yrs > yrs yrs 13yrs # of age classes Mean size 394mm 369 mm 383 mm Mature femaleh Shannon diversity Growth Male condition Female L infinity 769mm 732mm 688mm Male L infinity 644mm 602mm 606mm Female K 0.148/yr 0.162/yr 0.177/yr Mortality Adult Male 28% 32% 33% Maturity Male size-at- 50% mature 356mm 340mm 343mm Reproduction Male VFI 1.8% 1.3% 1.1% r rate of increase Abundance CPUE 450mm 2.0 /net /net 0.43/net

Lake Wanapitei Summer Profundal Index Netting (SPIN) Technical Report

Lake Wanapitei Summer Profundal Index Netting (SPIN) Technical Report Kimberley Tremblay Fisheries Biologist September 2007 755 Wallace Road, Unit 5 North Bay, ON P1B 8G4 Phone: (705) 472-7888 Fax: (705)