A Sport Fish Stock Assessment of Long Lake, Alberta, 2004

A Sport Fish Stock Assessment of Long Lake, Alberta, 2004 CONSERVATION REPORT SERIES

The Alberta Conservation Association is a Delegated Administrative Organization under Alberta s Wildlife Act. CONSERVATION REPORT SERIES 25% Post Consumer Fibre When separated, both the binding and paper in this document are recyclable

A Sport Fish Stock Assessment of Long Lake, Alberta, 2004 Greg Fortier and John Tchir Alberta Conservation Association Bag 900 26, Peace River Alberta, Canada T8S 1T4

Report Series Co editors GARRY J. SCRIMGEOUR DAVID FAIRLESS Alberta Conservation Association Alberta Conservation Association P.O. Box 40027 7 th Floor O.S. Longman Building Baker Centre Postal Outlet 6909 116 Street Edmonton, AB, T5J 4M9 Edmonton, AB, T6H 4P2 ISBN printed: 0 7785 4813 9 ISBN online: 0 7785 4814 7 Publication number: T/114. Disclaimer: This document is an independent report prepared by the Alberta Conservation Association. The authors are solely responsible for the interpretations of data and statements made within this report. Reproduction and Availability: This report and its contents may be reproduced in whole, or in part, provided that this title page is included with such reproduction and/or appropriate acknowledgements are provided to the authors and sponsors of this project. Suggested citation: Fortier, G.N. and Tchir, J.P. 2005. Sport fish stock assessment of Long Lake, Alberta, 2004. Data report, D 2005 018, produced by Alberta Conservation Association Bag 900 26, Peace River, Alberta, Canada. 20 pp. Cover photo credit: David Fairless Digital copies of conservation reports can be obtained from: Alberta Conservation Association P.O. Box 40027, Baker Centre Postal Outlet Edmonton, AB, T5J 4M9 Toll Free: 1 877 969 9091 Tel: (780) 427 5192 Fax: (780) 422 6441 Email: info@ab conservation.com Website: www.ab conservation.com i

EXECUTIVE SUMMARY In recent years, improved access to lakes that support populations of walleye (Sander vitreus) and northern pike (Esox lucius) has raised concerns about increased angling pressure on relatively unexploited fish populations. Strategies to maintain or recover northern pike and walleye populations, implemented by Alberta Sustainable Resource Development include changes in angling regulations to reduce fish mortality and increase recruitment. Regular evaluations of the abundance and structure of sport fish populations are necessary to evaluate the effectiveness of management strategies. We completed a stock assessment to quantify the size, age structure and growth of walleye, northern pike, lake whitefish (Coregonus clupeaformis) and yellow perch (Perca flavescens) in Long Lake, Alberta. Walleye accounted for 18.3% of the total catch. The total catch per unit effort (TCUE) of walleye was 6.65 fish/100 m 2 /24 hrs. Of all walleye sampled where sex could be determined, 43.7% were female. Fork lengths (FL) of walleye ranged from 214 to 529 mm (mean = 430.8 mm, n = 12) and age ranged from 3 to 18 years (mean = 9.6, n = 107). In contrast, northern pike accounted for 32.7% of the total catch with a TCUE of 11.81 fish/100 m 2 /24 hrs. Of all northern pike sampled where sex could be determined, 51.8% were female. Fork lengths of northern pike ranged from 223 to 889 mm (mean = 507.0 mm, n = 199), and age ranged from 1 to 15 years (mean = 6.4, n = 176). Lake whitefish accounted for 3.1% of the total catch with a TCUE of 1.13 fish/100 m 2 /24 hrs. Of all lake whitefish sampled where sex could be determined, 47.4% were female. Fork lengths of lake whitefish ranged from 314 to 531 mm (mean = 410.8 mm, n = 19) and age from 4 to 13 years (mean = 6.0, n = 18). Yellow perch accounted for 18.1% of the total catch with a TCUE of 6.53 fish/100 m 2 /24 hrs. Of all yellow perch sampled where sex could be determined, 67.9% were female. Fork length of yellow perch ranged from 121 to 247 mm (n = 110, mean = 161.7 mm) and ages from 3 to 11 years (mean = 4.3, n = 106). The stock assessment presented here allows fisheries managers to track potential effects of increased angling pressure on priority fish populations, like Long Lake, in the future. Increased monitoring of fish populations at Long Lake and other lakes in the Red Earth area will become more important with the development of the proposed highway extending from Red Earth to Fort McMurray. ii

Key words: walleye, northern pike, lake whitefish, yellow perch, gill netting, population structure, catch rates, maturity, length at age. iii

ACKNOWLEDGEMENTS We thank Nathan Carruthers, Clayton James, Tyler Johns, Paul Hvenegaard, Lorraine Sawdon, Kathleen Woodruff, and Kevin Yacyshyn and Garry Scrimgeour (Alberta Conservation Association) and Dave DeRosa and Travis Ripley (Alberta Sustainable Resource Development) for assisting with the delivery of this project and for reviewing earlier drafts of this report. iv

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TABLE OF CONTENTS EXECUTIVE SUMMARY... ii ACKNOWLEDGEMENTS...iv LIST OF FIGURES...vi LIST OF TABLES...vii 1.0 INTRODUCTION... 1 2.0 STUDY AREA... 1 3.0 MATERIALS AND METHODS... 3 3.1 Materials... 3 3.2 Methods... 3 3.3 Data analyses... 5 4.0 RESULTS... 6 4.1 Walleye... 6 4.2 Northern pike... 10 4.3 Lake Whitefish... 14 4.4 Yellow Perch... 16 4.5 Summary... 19 5.0 LITERATURE CITED... 20 v

LIST OF FIGURES Figure 1. Figure 2. Figure 3. Location of gill nets set in Long Lake, Alberta, in 2004. Inset shows the location of Long Lake in northern Alberta....2 Relation between maturity and age of female walleye from Long Lake, Alberta, 2004...7 Relation between maturity and fork length of female walleye from Long Lake, Alberta, 2004.....7 Figure 4. Fork length distribution of walleye from Long Lake, Alberta, 2004...8 Figure 5. Age distribution of walleye from Long Lake, Alberta, 2004...9 Figure 6. Figure 7. Figure 8. Figure 9 von Bertalanffy growth function fitted to male and female walleye from Long Lake, Alberta, 2004...9 Relation between maturity and age of female northern pike from Long Lake, Alberta, 2004.....10 Relation between maturity and fork length of female northern pike from Long Lake, Alberta, 2004...11 Felation between maturity and age of male northern pike from Long Lake, Alberta, 2004...11 Figure 10. Relation between maturity and fork length of male northern pike from Long Lake, Alberta, 2004....12 Figure 11. Fork length distribution of northern pike from Long Lake, Alberta, 2004..12 Figure 12. Age distributions of northern pike from index netting at Long Lake, Alberta, 2004...13 Figure 13. von Bertalanffy growth function fitted to male and female northern pike from Long Lake, Alberta, 2004....13 Figure 14. Fork length distribution of lake whitefish from Long Lake, Alberta, 2004..15 Figure 15. Age distribution of lake whitefish from Long Lake, Alberta, 2004...15 Figure 16. von Bertalanffy growth function fitted to male and female lake whitefish from Long Lake, Alberta, 2004...16 Figure 17. Fork length distributions of yellow perch from index netting at Long Lake, Alberta, 2004...17 Figure 18. Age distributions of yellow perch from Long Lake, Alberta, 2004....18 Figure 19. von Bertalanffy growth function fitted to male and female yellow perch sampled from Long Lake, Alberta, 2004...18 vi

LIST OF TABLES Table 1. Stratified sampling proportional to stratum surface area for index netting of Long Lake, Alberta, 2004...3 Table 2. Universal transverse mercator (UTM) coordinates (NAD 83, UTM zone 11) of the 10 gill nets deployed in Long Lake, Alberta, 2004...4 Table 3. Table 4. Table 5. Table 6. Mean (± 95% confidence intervals) catch rate (CPUE) (fish/100 m 2 /24 hrs) of walleye from Long Lake, Alberta....6 Mean (± 95% confidence intervals) catch rate (number of fish /100 m 2 /24 hrs) of northern pike from Long Lake, Alberta...10 Mean (±95% confidence interval ) catch rates (number of fish /100 m 2 /24 hrs) of lake whitefish from Long Lake, Alberta....14 Mean (±95% confidence interval) catch rates (number of fish /100 m 2 /24 hrs) of yellow perch from Long Lake, Alberta....16 vii

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1.0 INTRODUCTION Strategies to maintain or recover northern pike and walleye populations, implemented by Alberta Sustainable Resource Development, include changes in angling regulations to reduce fish mortality and increase recruitment. Regular evaluations of the abundance and structure of sport fish populations are necessary to evaluate the effectiveness of management strategies. Improved access, resulting from the development of new roads and improvements in existing roads into lakes in the Red Earth area, including Long Lake, in recent years has raised concerns about the impacts of increasing angling pressure on sport fish populations. In response, we completed a stock assessment to quantify the abundance, age and growth of walleye (Sander vitreus), northern pike (Esox lucius), lake whitefish (Coregonus clupeaformis) and yellow perch (Perca flavescens) between 17 and 24 June 2004 in Long Lake, Alberta. This information will aid in the development of management guidelines of the sport fishery at Long Lake. 2.0 STUDY AREA Long Lake is located approximately 41 km Northeast of Red Earth, Alberta (Figure 1). The Lake has a surface area of 539 ha, an average depth of 5 m and a maximum depth of 9 m. Access to the lake is provided by a gravel road. The lake supports natural populations of white sucker (Catostomus commersoni), longnose sucker (Catostomus catostomus), cisco (Coregonus artedi), lake whitefish, northern pike, burbot (Lota lota), yellow perch, and walleye. 1

Figure 1. Location of gill nets set in Long Lake, Alberta, 2004. Inset shows the location of Long Lake in northern Alberta. 2

3.0 MATERIALS AND METHODS 3.1 Materials Multi mesh benthic gill nets (net height and length = 2.4 m x 15.2 m) were used to capture fish. One net consisted of five panels each of a different mesh size. Mesh sizes of panels were 38, 63, 89, 114, and 140 mm (stretch measure) and were connected by bridals in sequential order. 3.2 Methods 3.2.1 Sampling design Information on the abundance, age and growth of sports fish were evaluated using a stratified random sampling design, with two depth strata. Sampling effort of these depth strata was allocated in proportion to lake surface area of the two depth strata (Table 1). A total of 10 gill nets were deployed between 17 and 24 June 2004 (Table 2). Locations of individual nets are provided in Figure 1. Sample sites where nets were deployed were randomly selected with a minimum distance of 500 m between all sites to minimize the effects of local depletion on catch rates. Nets were set for as close to 24 hours as logistically possible. Nets were set perpendicular to the shoreline where possible, without crossing depth intervals. The orientation of the largest or smallest mesh in relation to the shore was random. Nets were set at a minimum depth of 2 m. Table 1. Stratified sampling proportional to stratum surface area for index netting of Long Lake, Alberta, 2004. Depth Interval Proportion of lake surface area (%) Number of sites 0 5 m 46.5 5 5 10 m 53.5 5 Whole lake 100 10 3

Table 2. Universal transverse mercator (UTM) coordinates (NAD 83, UTM zone 11) of the 10 gill nets deployed in Long Lake, Alberta, 2004. Depth Interval (m) UTM Easting UTM Northing 0 5 643021.00 6288477.00 642394.00 6288426.00 646989.00 6288360.00 642646.00 6289387.00 643280.00 6289867.00 5 10 642407.00 6288825.00 644580.00 6289615.00 645592.21 6288891.05 643770.58 6288845.00 645128.00 6289513.00 3.2.2 Sample size Prospective power analysis (α = 0.1, power = 0.8) was used in advance in order to estimate the sample size required to detect an effect size of 10 fish per unit effort (fish/100m 2 /24hrs). This was performed using catch data from index netting in 2000 (Lucko 2001) for walleye, northern pike, and lake whitefish. These analyses indicated that 10 nets would be sufficient to detect a change in catch per unit effort of 10 fish/100 m 2 /24 hrs. Power analysis was also used during the course of the index netting in 2004 to ensure the minimal number of nets was set to attain the recommended level of precision. If the first 10 sites did not detect at least this effect size more samples would be required. Cost (e.g., fish mortalities, labour costs, non labour costs) and benefits (precision, reduced uncertainty) would be evaluated prior to proceeding with a larger sample size. The total number of sampled sites is shown in Table 1. 3.3.3 Data collection Biological data collected from all captured fish included: fork length (FL), total length (TL), weight, sex, maturity, and stomach contents. Ageing structures were also removed and aged following methods described by MacKay et al. (1990). Data on all 4

fish species were entered into the Provincial Governments Fisheries Management Information System (FMIS). Data on stomach content analyses are not presented in this report, but are included as part of the larger FMIS database as Inventory Project ID 6329. 3.3 Data analyses 3.3.1 Catch per unit effort We quantified the abundance of fish as catch per unit effort (CPUE), calculated as the number of fish captured/100 m 2 /24 hrs. This was calculated for each species caught at each sample site. Catch per unit effort is reported as the mean and 95% confidence interval (95% CI) of all sample sites for each species. The mean CPUE and 95% CI for each depth stratum were reported as well as the overall mean. Total catch per unit effort (TCUE), calculated as the total number of fish/100 m 2 /24 hrs, was also reported for each species. 3.3.2 Maturity The ratio of mature to immature fish in each respective category was assessed based on age and length. Maturity was reported in terms of the age or length at which approximately 50% of fish were mature. 3.3.3 Length and age distributions Fork lengths (FL) were separated into 20 mm length classes (10 mm classes for yellow perch) to display the length distribution of fish captured. Length and age distributions were displayed as CPUE for each length and age class. Fork length and TL measurements of fish from index netting and the angler survey were fitted to linear regression equations. The TL for walleye and northern pike can be estimated from the FL by the following equations: Walleye: TL (mm) = 1.046 FL + 6.94 (R 2 = 0.997, n =112) Northern pike: TL (mm) = 1.038 FL + 11.30 (R 2 = 0.998, n =197). 5

3.3.4 Von Bertalanffy growth function Age and length data for males and females were fitted separately to the von Bertalanffy growth function. When sample sizes were inadequate to derive separate growth models for males and females, data for both sexes were combined and models derived using the pooled data. The von Bertalanffy growth function is a non linear equation that explains growth using the three parameters of length infinity, growth, and age at length zero. Length infinity (L ) represents the asymptote or the theoretical maximum length that can be achieved. This length is often lower than the true maximum size due to small sample sizes of very large fish. Fork length was the measurement used to describe length. The parameter representing growth is K, which is defined as the rate at which the fish approaches L. Higher values of K represent faster growth and are usually associated with a lower L. The third parameter of the von Bertalanffy growth function is t0, the hypothetical time when the fish was size zero. Length at age zero can be highly variable with small sample sizes of small fish. In addition, application of age at length zero has very little practical application and was therefore fixed at zero. 4.0 RESULTS 4.1 Walleye Walleye accounted for 18.3% of the total catch (112 of 609 fish). The TCUE was 6.65 fish/100 m 2 /24 hrs. Mean CPUE, sample size (n), and 95% CI calculated from index netting in 2004 are shown for each depth interval in Table 3. Table 3. Mean (± 95% confidence intervals) catch rate (CPUE) (fish/100 m 2 /24 hrs) of walleye from Long lake, Alberta. n = the number of sample sites for each depth strata. Depth Range (m) Mean CPUE (fish/100 m 2 /24 hrs) 95% confidence interval (±) n 0 5 m 9.59 7.18 5 5 10 m 4.61 7.77 5 Whole lake 7.10 4.48 10 6

Analyses of maturity data suggested that the age and length at which 50% of female walleye were mature ranged between 7 and 10 years (Figure 2) and 400 to 450 mm FL (Figure 3), respectively. All male walleye captured were mature. 100% 80% 1 Maturity 60% 40% 1 13 1 9 13 5 1 Mature Immature 20% 1 0% 3 6 7 8 10 11 12 13 Age (years) Figure 2. Relation between maturity and age of female walleye from Long Lake, Alberta 2004. Sample sizes for each class are represented in each respective bar. 100% 1 80% 4 Maturity 60% 40% 1 1 10 19 7 Mature Immature 20% 4 0% 250 350 400 450 500 550 Fork length (mm) Figure 3. Relation between maturity and fork length of female walleye from Long Lake, Alberta 2004. Sample sizes for each class are represented in each respective bar. 7

Of all walleye sampled where sex could be determined, 43.7% were female. Fork length of males ranged from 351 to 529 mm (mean = 427.5 mm, n = 63) while that of females ranged from 214 to 525 mm (mean = 435.0 mm, n = 49). The mean FL of all walleye sampled was 430.8 mm (n = 112) (Figure 4). 1.2 1.0 0.8 0.6 0.4 0.2 0.0 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 Catch per unit effort Fork length (mm) Figure 4. Fork length distribution of walleye from Long Lake, Alberta, 2004 (n = 112). Y axis is catch per unit effort (i.e., number of fish/100 m 2 /24 hrs). Age of males ranged from 6 to 18 years (mean = 10.1, n = 60) while females ranged from 3 to 13 years (mean = 9.1, n = 47). The mean age of all walleye sampled in 2004 was 9.6 years (n =107; Figure 5). The von Bertalanffy growth function was used to describe growth of walleye. Figure 6 shows female and male data from 2004 fitted to the von Bertalanffy growth function. 8

Catch per unit effort 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Age (years) Figure 5. Age distribution of walleye from Long Lake, Alberta, 2004 (n = 107). Y axis is catch per unit effort (i.e., fish/100 m 2 /24 hrs). 700 600 l = l (1 e k (t) ) Fork length (mm) 500 400 300 200 100 0 0 5 10 15 20 Age (years) Figure 6. von Bertalanffy growth function fitted to male and female walleye from Long Lake, Alberta, 2004 (Males: n = 60, L = 488.1, k = 0.228; females: n = 47, L = 584.3, k = 0.161). 9

4.2 Northern pike Northern pike accounted for 32.7% of the total catch (199 of 609 fish). The TCUE was 11.81 fish/100 m 2 /24 hrs. Mean CPUE, sample size, and 95% CI calculated from index netting in 2004 are shown for each depth interval in Table 4. Table 4. Mean (± 95% confidence intervals) catch rate (number of fish /100 m 2 /24 hrs) of northern pike from Long Lake, Alberta. n = the number of sample sites for each depth strata. Depth Mean CPUE (fish/100 m 2 /24 hrs) 95% confidence interval (±) n 0 5 m 14.58 9.26 5 5 10 m 9.17 5.74 5 Whole lake 11.88 4.65 10 Analyses of maturity data showed that the point of 50% maturity (age or length where half of fish become mature) appears to occur between 4 and 5 years (Figure 7) or between 450 and 500 mm FL (Figure 8) for female northern pike. Males appear to mature between 2 and 3 years (Figure 9) or between 350 and 450 mm FL (Figure 10). 100% 80% 3 8 Maturity 60% 40% 20% 1 14 8 7 17 12 3 3 3 1 Mature Immature 0% 1 1 3 4 5 7 8 9 10 11 12 15 Age (years) Figure 7. Relation between maturity and age of female northern pike from Long Lake, Alberta, 2004. Sample sizes for each class are represented in each respective bar. 10

100% 80% 2 5 \ Maturity 60% 40% 20% 0% 1 3 13 12 3 18 2 18 12 7 3 1 1 Mature Immature 350 400 450 500 550 600 650 700 750 850 900 Fork length (mm) Figure 8. Relation between maturity and fork length of female northern pike from Long Lake, Alberta 2004. Sample sizes for each class are represented in each respective bar. 100% 80% Maturity 60% 40% 1 1 13 17 8 2 6 9 9 9 4 3 Mature Immature 20% 0% 6 2 1 2 3 4 5 6 7 8 9 10 11 12 Age (years) Figure 9. Relation between maturity and age of male northern pike from Long Lake, Alberta, 2004. Sample sizes for each class are represented in each respective bar. 11

100% Maturity 80% 60% 40% 1 1 2 5 24 16 16 18 4 Mature Immature 20% 0% 1 4 4 250 300 350 400 450 500 550 600 650 Fork Length (mm) Figure 10. Relation between maturity and fork length of male northern pike from Long Lake, Alberta, 2004. Sample sizes for each class are represented in each respective bar. Of all northern pike sampled where sex could be determined, 51.8% were females. Male FL ranged from 223 to 627 mm (n = 96, mean = 477.6 mm) while female FL ranged from 328 to 889 mm (n = 103, mean = 534.5 mm). The mean FL of all northern pike sampled was 507.0 mm (n = 199). Figure 11 shows the FL distributions of northern pike captured from Long Lake in 2004. Catch per unit effort 1.2 1.0 0.8 0.6 0.4 0.2 0.0 220 260 300 340 380 420 460 500 540 580 620 660 700 740 780 820 860 900 940 Fork length (mm) Figure 11. Fork length distribution of northern pike from Long Lake, Alberta, 2004 (n = 199). Y axis is catch per unit effort (i.e., Number of fish/100 m 2 /24 hrs). 12

Males ranged in age from 1 to 12 years (n = 90, mean = 6.1) while females ranged from 3 to 15 years (n = 86, mean = 6.6). The mean age of all northern pike sampled in 2004 was 6.4 years (n = 176) (Figure 12). The von Bertalanffy growth function was used to describe growth of northern pike. Figure 13 shows data for female and males fitted to the von Bertalanffy growth function. Catch per unit effort 3.0 2.5 2.0 1.5 1.0 0.5 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Age (years) Figure 12. Age distributions of northern pike from index netting at Long Lake, Alberta, 2004 (n = 176). Y axis is catch per unit effort (i.e., number of fish/100 m 2 /24 hrs). 1000 900 l = l (1 e k(t) ) 800 Fork length (mm) 700 600 500 400 300 200 100 0 0 5 10 15 20 Age (years) Figure 13. von Bertalanffy growth function fitted to male and female northern pike from Long Lake, Alberta, 2004 (Males: n = 90, L = 576.8, k = 0.360; Females: n = 86, L = 709.6, k = 0.237). 13

4.3 Lake Whitefish Lake whitefish accounted for 3.1% of the total catch (19 of 609 fish). The TCUE was 1.13 fish/100 m 2 /24 hrs. Mean CPUE, sample size, and 95% CI calculated from index netting in 2004 are shown for each depth interval in Table 5. Table 5. Mean (±95% confidence interval ) catch rates (number of fish /100 m 2 /24 hrs) of lake whitefish from Long Lake, Alberta. n = number of nets set in each depth strata. Depth Mean CPUE (fish/100 m 2 /24 hrs) 95% confidence interval (±) n 0 5 m 1.07 2.04 5 5 10 m 1.33 1.4 5 Whole lake 1.2 0.96 10 Of all lake whitefish sampled where sex could be determined, 47.4% were female. Male FL ranged from 314 to 531 mm (n =1 0, mean = 395.0 mm) while females ranged from 316 to 521 mm (n = 9, mean = 428.3 mm). The mean FL of all lake whitefish sampled was 410.8 mm (n = 19) (Figure 14). Points of 50% maturity could not be determined because low numbers of immature lake whitefish were captured; the only immature fish was of a 4 year old which measured 380 mm. 14

0.3 0.2 0.2 0.1 0.1 0.0 340 360 380 400 420 440 460 480 500 520 540 560 Catch per unit effort 580 600 620 640 Fork length (mm) Figure 14. Fork length distribution of lake whitefish from Long Lake, Alberta, 2004 (n = 19). Y axis catch per unit effort (i.e., number of fish/100 m 2 /24 hrs). Males ranged in age from 4 to 10 years (n = 9, mean = 5.4) while females ranged from 4 to 13 years (n = 9, mean = 6.6). The mean age of all lake whitefish sampled in 2004 was 6.0 years (n = 18). Figure 15 shows the 2004 lake whitefish age distribution. The von Bertalanffy growth function was used to describe growth of lake whitefish. As a result of low sample size the von Bertalanffy growth function was fitted to male and female data combined (Figure 16). Catch per unit effort 0.6 0.5 0.4 0.3 0.2 0.1 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Age (years) Figure 15. Age distribution of lake whitefish from Long Lake, Alberta, 2004 (n = 18). Y axis is catch per unit effort (i.e., fish/100 m 2 /24 hrs). 15

600 500 l = l (1 e k(t) ) Fork length (mm) 400 300 200 100 0 0 5 10 15 20 Age (years) Figure 16. von Bertalanffy growth function fitted to male and female lake whitefish from Long Lake, Alberta, 2004 (n = 18, L = 546.7, k = 0.264). 4.4 Yellow Perch Yellow perch accounted for 18.1% (n = 110) of the total catch. The TCUE was 6.53 fish/100 m 2 /24 hrs. Mean CPUE, sample size, and 95% CI calculated from index netting in 2004 are shown for each depth interval in Table 6. Table 6. Mean (±95% confidence interval) catch rates (number of fish /100 m 2 /24 hrs) of yellow perch from Long Lake, Alberta. n = number of nets set in each depth strata. Depth Mean CPUE fish/100 m 2 /24 hrs 95% confidence interval (±) n 0 5 m 8.77 6.55 5 5 10 m 4.80 3.61 5 Whole lake 6.80 3.23 10 16

Of all yellow perch sampled where sex could be determined, 67.9% were female in 2004. Male FL ranged from 125 to 233 mm (n = 35, mean = 159.1 mm) and females from 121 to 247 mm (n = 74, mean = 163.2 mm). The mean FL of all yellow perch sampled was 161.7 mm (n = 110). Figure 17 shows the fork length distributions from 2004. 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 Catch per unit effort Fork length (mm) Figure 17. Fork length distributions of yellow perch from index netting at Long Lake, Alberta, 2004 (n = 110). Y axis is catch per unit effort (i.e., fish/100m 2 /24 hrs). Male yellow perch ranged in age from 3 to 9 years (n = 34, mea n = 4.2), while females ranged from 3 to 11 years (n = 72, mean = 4.3). The mean age of all yellow perch sampled in 2004 was 4.3 years (n =1 06) (Figure 18). The von Bertalanffy growth function was used to describe growth of yellow perch. Figure 19 shows female and male data fitted to the von Bertalanffy growth function. 17

Catch per unit effort 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 1 2 3 4 5 6 7 8 9 10 11 12 Age (years) Figure 18. Age distributions of yellow perch from Long Lake, Alberta, 2004 (n = 106). Y axis is catch per unit effort (i.e., number of fish/100 m 2 /24 hrs). 300 l = l (1 e k (t) ) Fork length (mm) 200 100 0 0 2 4 6 8 10 12 14 Age (years) Figure 19. von Bertalanffy growth function fitted to male and female yellow perch sampled from Long Lake, Alberta, 2004 (Males: n = 34, L = 248.3, k = 0.255; Females: n = 72, L = 278.6, k = 0.220). 18

4.5 Summary To assist with the recovery of declining stocks, minimum size limits were implemented for walleye and northern pike across Alberta several years ago. At lakes where fishing pressure is relatively high the size distribution of walleye and northern pike tends to be truncated at or near the minimum size limit for angler harvest, consistent with disproportionate angling induced mortality. In Long Lake, angling mediated mortality of walleye and northern pike does not appear to have truncated the size distribution at the minimum size limit (walleye, 50 cm TL or 47.1 cm FL; northern pike, 70 cm TL or 66.4 cm FL); CPUE is not substantially lower for fish larger than these size limits. Results from an angler survey completed in 2004 (Fortier and Tchir 2004) showed that angling pressure was very low during the summer months. Low angling pressure and the current size distributions of walleye and northern pike suggest that angler harvest is not a major concern at this time. Improved access (upgraded and new roads) into lakes in the Red Earth area, including Long Lake, in recent years has raised concerns about the potential for increased angling pressure. The results of the present study provide important baseline information that can be used by resource managers to quantify the effects of increases in angling effort mediated by increased access to Long Lake forecasted to occur over the next decade. Increased monitoring of fish populations at Long Lake and other lakes in the Red Earth area will become more important with the development of the proposed highway extending from Red Earth to Fort McMurray. 19

5.0 LITERATURE CITED Berry D.K. 1995. Alberta s walleye management and recovery plan. Alberta Environmental Protection, Natural Resources Service. Number T/310. Edmonton, Alberta. 32 pp. Berry D.K. 1999. Alberta s northern pike management and recovery plan. Alberta Environmental Protection, Natural Resources Service. Number T/459. Edmonton, Alberta. 22 pp. Fortier, G., and J. Tchir. 2004. Assessment of the summer sport fishery for walleye (Sander vitreus) and northern pike (Esox lucius) at Graham Lake, Alberta, 2004. Alberta Conservation Association, Peace River, Alberta. Lucko B. 2001. Lake monitoring program 2001 results Gods Lake. Unpublished report prepared by Alberta Conservation Association, Peace River, Alberta. Mackay, W.C., G.R. Ash, and H.J. Norris. 1990. Fish ageing methods for Alberta. R.L. & L. Environmental Services Ltd. In association with Alberta Fish and Wildlife Division and University of Alberta, Edmonton. 20

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The Alberta Conservation Association acknowledges the following partner for their generous support of this project