Status of Sport Fish in North Wabasca Lake, , 2006

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CONSERVATION REPORT

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Status of Sport Fish in North Wabasca Lake, Alberta, 2006

Nathan Carruthers and Tyler Johns Alberta Conservation Association Bag 900‐26 96 Avenue , Alberta, Canada T8S 1T4

Report Series Co‐editors PETER AKU KELLEY KISSNER Alberta Conservation Association 50 Tuscany Meadows Cres NW #101, 9 Chippewa Rd Calgary, AB T3L 5K9 Sherwood Park, AB T8A 6J7

Conservation Report Series Type Data, Technical

ISBN printed: 978‐0‐7785‐8185‐7 ISBN online: 978‐0‐7785‐8186‐4 Publication No.: T/208

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: Carruthers, N., and T. Johns. 2007. Status of sport fish in North Wabasca Lake, Alberta, 2006. Data Report, D‐2007‐012, produced by the Alberta Conservation Association, Peace River, Alberta, Canada. 26 pp + App.

Cover photo credit: David Fairless

Digital copies of conservation reports can be obtained from: Alberta Conservation Association #101, 9 Chippewa Rd Sherwood Park, AB T8A 6J7 Toll Free: 1‐877‐969‐9091 Tel: (780) 410‐1998 Fax: (780) 464‐0990 Email: info@ab‐conservation.com Website: www.ab‐conservation.com

i EXECUTIVE SUMMARY

Strategies implemented by Alberta Sustainable Resource Development (ASRD) to manage sport fish populations in Alberta require ongoing monitoring to evaluate their effectiveness. The present study was conducted on North Wabasca Lake to generate quantitative data on abundance, population structure and growth of four major species; (Sander vitreus), northern pike ( lucius), (Perca flavescens) and ( clupeaformis).

A total of 822 fish were captured during the 2006 survey. Northern pike was the most abundant sport fish, accounting for 19% of the catch, and yellow perch was the least abundant, accounting for 5% of the catch.

A total of 99 walleye were caught in the 2006 stock assessment. Mean catch‐per‐unit‐ effort (CPUE) for walleye ranged from 3.73 to 8.33 fish/100 m2/24 h, with a total catch‐ per‐unit‐effort (TCUE) of 5.67 fish/100 m2/24 h. Of the 99 walleye sampled, 63% were female and 37% were male resulting in a female to male sex ratio of 1.69:1. Total length (TL) of females ranged from 122.6 to 612.6 mm with a mean length (± SD) of 392.8 ± 118.3 mm (n = 61). Males ranged in length from 125.8 to 475.0 mm with a mean length of 365.4 ± 93.0 mm (n = 36). Male walleye ranged in age from 2 to 13 y with a mean age (± SD) of 6.84 ± 3.14 y (n = 31). Females ranged in age from 2 to 15 y with a mean age of 5.98 ± 2.97 y (n = 55). Overall, mean age of the catch was 6.29 ± 3.04 y (n = 86).

A total of 158 northern pike were caught in the 2006 stock assessment. Mean CPUE for northern pike ranged from 6.83 to 10.88 fish/100 m2/24 h, with a TCUE of 9.06 fish/100 m2/24 h. Of the 158 northern pike sampled, 74% were female and 26% were male resulting in a female to male sex ratio of 2.85:1. Total length of females ranged from 438.4 to 912.5 mm with a mean length of 696.5 ± 114.65 mm (n = 117). Males ranged in length from 439.4 to 739.2 mm with a mean length of 566.4 ± 87.09 mm (n = 41). Males ranged in age from 3 to 12 y with a mean age of 5.74 ± 2.27 y (n = 39). Females ranged in age from 3 to 11 y with a mean age of 6.59 ± 1.93 y (n = 114). Overall, mean age of the catch was 6.38 ± 2.05 y (n = 153).

A total of 43 yellow perch were caught in the 2006 stock assessment. Mean CPUE for yellow perch ranged from 1.18 to 4.06 fish/100 m2/24 h with a total CPUE of 2.47

ii fish/100 m2/24 h. Of the 39 yellow perch sampled where sex could be determined, 69.2% (n = 27) were female and 30.8% (n = 12) were male resulting in a female to male sex ratio of 2.25:1. Total length of females ranged from 99.0 to 276.7 mm with a mean length of 197.2 ± 64.9 mm (n = 27). Males ranged in length from 105.3 to 247.2 mm with a mean length of 179.8 ± 46.2 mm (n = 12). Male yellow perch ranged in age from 2 to 9 y with a mean age of 5.00 ± 2.65 y (n = 7). Females ranged in age from 1 to 9 y with a mean age of 6.15 ± 2.61 y (n = 13). Overall, mean age of the catch was 5.32 ± 2.85 y (n = 22).

A total of 100 lake whitefish were caught in the 2006 stock assessment. Mean CPUE for lake whitefish ranged from 4.17 to 6.68 fish/100 m2/24 h with a TCUE of 5.74 fish/100 m2/24 h. Of the 99 lake whitefish sampled where sex could be determined, 44% (n = 44) were female and 56% (n = 55) were male resulting in a female to male sex ratio of 0.80:1. Total length of females ranged from 257.4 to 534.8 mm with a mean length of 464.4 ± 68.83 mm (n = 44). Males ranged in length from 273.6 to 545.6 mm with a mean length of 469.1 ± 57.14 mm (n = 55). Males ranged in age from 2 to 15 y with a mean age of 8.75 ± 3.15 y (n = 55). Females ranged in age from 2 to 14 y with a mean age of 8.44 ± 3.66 y (n = 43). Overall, mean age of the catch was 8.54 ± 3.43 y (n = 99).

The results of this study provide important baseline information that can be used by resource managers to quantify the effects of anticipated increases in angling pressure on sport fish populations in North Wabasca Lake.

Key words: walleye, northern pike, lake whitefish, yellow perch, benthic gill net, North Wabasca Lake, catch‐per‐unit‐effort.

iii ACKNOWLEDGEMENTS

This work was funded by the Alberta Conservation Association. We thank Greg Fortier and Ryan Hermanutz for assisting with data collection and Paul Hvenegaard for reviewing earlier drafts of this report. We also thank staff from the Wabasca fire staging camp for their hospitality and excellent food.

iv

TABLE OF CONTENTS

EXECUTIVE SUMMARY...... ii ACKNOWLEDGEMENTS...... iv TABLE OF CONTENTS ...... v LIST OF FIGURES...... vi LIST OF TABLES...... vii LIST OF APPENDICES ...... viii 1.0 INTRODUCTION ...... 1 2.0 STUDY AREA...... 1 3.0 MATERIALS AND METHODS ...... 3 3.1 Sampling design ...... 3 3.2 Data collection...... 4 3.3 Data analysis ...... 4 4.0 RESULTS ...... 6 4.1 Walleye...... 6 4.2 Northern pike...... 11 4.3 Yellow perch...... 16 4.4 Lake whitefish...... 20 4.5 Summary...... 25 5.0 LITERATURE CITED ...... 26 6.0 APPENDIX...... 27

v LIST OF FIGURES

Figure 1. Map of North Wabasca Lake showing gill net locations in 2006...... 2 Figure 2. Length distributions of male and female walleye captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 9 Figure 3. Age distributions of male and female walleye captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 10 Figure 4. von Bertalanffy plots for male and female walleye from North Wabasca Lake, Alberta, 2006...... 11 Figure 5. Length distributions of male and female northern pike captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 14 Figure 6. Age distributions of male and female northern pike captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 15 Figure 7. von Bertalanffy plots for male and female northern pike from North Wabasca Lake, Alberta, 2006...... 16 Figure 8. Length distributions of male and female yellow perch captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 18 Figure 9. Age distributions of male and female yellow perch captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 19 Figure 10. von Bertalanffy plots for yellow perch from North Wabasca Lake, Alberta, 2006...... 20 Figure 11. Length distributions of male and female lake whitefish captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 23 Figure 12. Age distributions of male and female lake whitefish captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 24 Figure 13. von Bertalanffy plots for male and female lake whitefish from North Wabasca Lake, Alberta, 2006...... 25

vi LIST OF TABLES

Table 1. Fish species present in North Wabasca Lake, Alberta...... 3 Table 2. Distribution of fish sampling effort by depth strata in North Wabasca Lake, Alberta, 2006...... 4 Table 3. Proportion of mature walleye in each length class captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 7 Table 4. Proportion of mature walleye in each age class captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 8 Table 5. Proportion of mature northern pike in each length class captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 12 Table 6. Proportion of mature northern pike in each age class captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 13 Table 7. Proportion of mature yellow perch in each age class captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 17 Table 8. Proportion of mature yellow perch in each length class captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 17 Table 9. Proportion of mature lake whitefish in each age class captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 21 Table 10. Proportion of mature lake whitefish in each length class captured during the 2006 stock assessment at North Wabasca Lake, Alberta...... 22

vii LIST OF APPENDICES

Appendix 1. Universal transverse mercator coordinates of test‐netting locations on North Wabasca Lake, Alberta 2006...... 27 Appendix 2. Test netting field data collection sheet...... 28

viii 1.0 INTRODUCTION

Strategies implemented by Alberta Sustainable Resource Development (ASRD) to maintain or recover walleye and northern pike include changes in angling regulations that are designed to reduce fish mortality and increase recruitment (Berry 1995, 1999). Regular evaluations of the abundance and structure of sport fish populations are necessary to evaluate the effectiveness of management strategies.

The growth and development of northern Alberta has resulted in increased angling pressure on the region’s lakes. Changes in angler pressure have raised concerns about the potential impacts on sport fish populations in North Wabasca Lake, Alberta. To assess impacts of changing angling pressure, Alberta Conservation Association conducted a lentic stock assessment survey on North Wabasca Lake. Data were collected between 15 and 19 September 2006 to quantify abundance, age and growth of the four major sport fish species: walleye (Sander vitreus), northern pike (Esox lucius), yellow perch (Perca flavescens) and lake whitefish (Coregonus clupeaformis).

2.0 STUDY AREA

North Wabasca Lake is located approximately 100 km northeast of Slave Lake, Alberta (318756 Easting 6216702 Northing, UTM Zone 12; Figure 1). It has a surface area of 12,200 ha, a mean depth of 5.8 m and a maximum depth of 15.8 m. Access to the lake is via a paved highway to the town of Wabasca, followed by short gravel roads to several access sites around the lake. The lake is most easily accessed by the maintained boat launches on the east side of the lake.

1 !( ±

!( !( !(

!( !(

!( !(

!(

!(

!( !( !( Legend

!( Sampling locations !( 0 - 5 m depth interval 5 - 15 m depth interval !( > 15 m depth interval

!(

[_

Slave Lake

012340.5

Kilometers

Figure 1. Map of North Wabasca Lake showing gill net locations in 2006. Inset is a map of Alberta indicating the location of the lake in the province.

2 In addition to walleye, northern pike, yellow perch and lake whitefish, North Wabasca Lake supports natural populations of several other fish species (Table 1).

Table 1. Fish species present in North Wabasca Lake, Alberta.

Common Name Scientific name Walleye Sander vitreus Northern Pike Esox lucius Lake Whitefish Coregonus clupeaformis Yellow Perch Perca flavescens Lota lota Coregonus artedi Longnose Sucker Catostomus catostomus White Sucker Catostomus commersoni Spottail Shiner Notropis hudsonius

3.0 MATERIALS AND METHODS

3.1 Sampling design

Sixteen multi‐mesh benthic gill nets were used to capture fish (Appendix 1). Each net measured 1.8 m deep by 61.0 m long and consisted of eight 7.6 m panels of different mesh sizes (stretched mesh) 25, 38, 51, 64, 76, 102, 127, and 152 mm sewn together in sequential order.

Sampling sites were selected in a stratified random sampling design, with two depth strata (0 to 5 m and 5 to 15 m); water deeper than 15 m was not sampled. Sampling effort was allocated proportionately to surface area of the two depth strata (Table 2). Sampling sites were randomly selected with a minimum distance of 500 m between all sites. Nets were set at depths ≥ 2 m and ≤ 15 m for approximately 24 h. Nets were set perpendicular to the shoreline. If a net extended beyond its depth stratum, it was reset at an angle in order to keep the entire net within the stratum. The orientation of the largest or smallest mesh size in relation to the shore was random.

3 Table 2. Distribution of fish sampling effort by depth strata in North Wabasca Lake, Alberta, 2006.

Depth interval (m) Proportion of lake surface area (%) Number of sites 0 to 5 56 9 5 to 15 43 7

3.2 Data collection

Biological data collected from all captured fish included: fork length (FL), total length (TL) and weight. Sex and maturity were determined through internal examination of deceased fish. Gonad weight was recorded for all mature female walleye, as requested by ASRD. Ageing structures were removed from deceased fish and were aged following methods in Mackay et al. (1990). Cleithra were collected to age northern pike, opercular bones and dorsal fin rays were collected to age yellow perch, and pelvic fin rays were collected to age walleye. All data were entered into the Government of Alberta Fisheries Management Information System (FMIS), Project Location ID 7446.

3.3 Data analysis

The abundance of each species, expressed as catch‐per‐unit‐effort (CPUE, fish/100 m2 of net/24 h) was calculated at each sampling site and used to calculate the mean CPUE (+ 95% confidence interval). CPUE values were reported for each depth stratum as well as a grand mean for depth strata combined. Total catch‐per‐unit‐effort (TCUE) is the total catch of each fish species over the total effort applied. Fisheries managers compare catch rates (CPUE and TCUE) to those on similar lakes, as well as monitor changes in catch rates over time in a particular lake.

Length‐frequency and age‐frequency distributions were used to examine the population structure of each species. Distributions of length and age were shown in relation to CPUE for each length class or age interval. Total length distributions were displayed in 20 mm length classes for walleye, northern pike and lake whitefish. Length distributions for yellow perch were displayed in 10 mm length classes.

We established relations between FL and TL for walleye, northern pike, yellow perch and lake whitefish from fish captured in this study. In order to reduce sampling time,

4 TL was not measured for all fish. However, TL is required by fisheries managers because walleye and northern pike have length restrictions on harvest which are based on TL. To determine TL of fish not measured, we plotted FL and TL measurements of individual fish, where both were recorded, and used this data to fit the following linear regression models to northern pike and yellow perch.

Northern :pike TL = FL + ;07.15)(0356.1 R 2 ,996.0( n == )59 )18,999.0(;99.0)(0428.1 :perch Yellow :perch TL = FL + R 2 n == )18,999.0(;99.0)(0428.1

Fish maturity was described as the age at which 50% of fish were mature. The length at which 50% of fish were mature was also reported. Fish growth rate was described using the von Bertalanffy (1938) growth model:

k ‐ (t‐ )t = 0 Lt ∞ (1L ‐ )e where:

Lt = length at age t,

L∞ = the asymptote or final maximum size, k = the rate at which the growth curve approaches the asymptote, and

t0 = a time scaler, the hypothetical time when the fish was size zero.

To account for sexual variation in growth rate, the von Bertalanffy model was fitted separately for male and female fish. The parameter used to estimate growth in the von Bertalanffy model is k, i.e., the rate at which the fish approaches maximum size (L∞). Higher values of k represent faster growth and are usually associated with a lower L∞.

Due to small sample sizes of small fish, t0 was fixed at zero to reduce bias in the growth function.

5 4.0 RESULTS

4.1 Walleye

Walleye accounted for 12% of the total catch (99 of 822 fish captured). TCUE was 5.67 fish/100 m2/24 h. Mean CPUE (± 95% CI) ranged from 3.73 ± 1.51 fish/100 m2/24 h (n = 9) in the 0 to 5 m depth interval to 8.33 ± 2.16 fish/100 m2/24 h (n = 7) in the 5 to 15 m interval. The grand mean CPUE was 5.74 ± 1.67 fish/100 m2/24 h (n = 16).

The proportion of mature walleye in each age and length class is shown in Tables 2 and 3. While sample sizes of each age class were insufficient to determine the point of 50% maturity, the data showed this likely occurs earlier than age‐8 for both males and females. The data also showed that 50% of male walleye are likely mature before they reach 430 mm TL. Small sample sizes of females in each length category were insufficient to determine the point of 50% maturity. However, the data suggested that 50% of female walleye are likely not mature before they reach 430 mm TL.

Of the 97 walleye sampled where sex could be determined, 62.8% (n = 61) were female and 37.1% (n = 36) were male resulting in a female to male sex ratio of 1.69:1. Total length of females ranged from 122.6 to 612.6 mm with a mean length (± SD) of 392.8 ± 118.3 mm (n = 61; Figure 2), whereas total length of males ranged from 125.8 to 475.0 mm with a mean length of 365.4 ± 93.0 mm (n = 36; Figure 2).

6 Table 2. Proportion of mature walleye in each length class captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Total length Males Females (mm) % mature n % mature n 100 ‐ ‐ ‐ ‐ 120 0 1 0 2 140 ‐ ‐ ‐ ‐ 160 0 1 ‐ ‐ 180 0 1 0 1 200 0 1 0 3 220 ‐ ‐ 0 2 240 0 1 0 3 260 0 1 0 1 280 0 2 0 1 300 0 2 0 2 320 ‐ ‐ 0 5 340 20 5 0 3 360 100 2 0 5 380 100 1 0 4 400 100 6 0 5 420 100 2 0 1 440 100 6 33 3 460 100 3 100 1 480 100 1 60 5 500 ‐ ‐ 100 4 520 ‐ ‐ 100 2 540 ‐ ‐ 100 5 560 ‐ ‐ 100 2 580 ‐ ‐ ‐ ‐ 600 ‐ ‐ 100 1 620 ‐ ‐ ‐ ‐

7 Table 3. Proportion of mature walleye in each age class captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Age Males Females (y) % mature n % mature n 1 ‐ ‐ ‐ ‐ 2 0 1 0 7 3 33 3 0 4 4 17 6 0 9 5 100 3 0 9 6 100 1 0 4 7 80 5 67 6 8 100 4 83 6 9 100 2 100 1 10 ‐ ‐ 100 4 11 100 3 100 4 12 100 1 ‐ ‐ 13 100 2 ‐ ‐ 14 ‐ ‐ ‐ ‐ 15 ‐ ‐ 100 1 16 ‐ ‐ ‐ ‐

8 0.50 Males (n = 36) Females (n = 61) 0.40 ) 2

0.30 hours/100m

0.20 (fish/24

CPUE 0.10

0.00 100 140 180 220 260 300 340 380 420 460 500 540 580 620

Predicted Total Length (mm)

Figure 2. Length distributions of male and female walleye captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Males ranged in age from 2 to 13 y with a mean (± SD) of 6.84 ± 3.14 y (n = 31; Figure 3), whereas females ranged in age from 2 to 15 y with a mean age of 5.98 ± 2.97 y (n = 55; Figure 3). Overall, mean age of the catch was 6.29 ± 3.04 y (n = 86). The age‐4 and 5 cohorts were equally the most abundant year‐classes for female walleye, each representing 16.4% of all females captured (n = 9 each). Age‐4 males were most abundant, representing 19.4% of all males captured (n = 6). Age‐4 females had a mean TL of 364.8 ± 28.1 m (n = 9), whereas mean TL of age‐5 females was 372.4 ± 31.9 mm (n = 9). Age‐4 males had a mean TL of 335.3 ± 27.2 mm (n = 6). With average total lengths below the legal harvest size of 43 cm, both the age‐4 and 5 females and the age‐4 male cohorts were not yet susceptible to angler harvest.

9 0.60 Females (n = 55) ) 2 0.50 Males (n = 31)

0.40 hours/100m 0.30

0.20 (fish/24

0.10 CPUE

0.00 1 2 3 4 5 6 7 8 9 10111213141516

Age

Figure 3. Age distributions of male and female walleye captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

When fitted to the von Bertalanffy growth function, male walleye had an L∞ of 460.6

mm TL and a growth coefficient k of 0.350 (n = 31; Figure 4). Females had an L∞ of 603.8 mm TL and a growth coefficient k of 0.220 (n = 55; Figure 4).

10 700

600

500 (mm) 400 Length 300 Total 200

100

0 0246810121416

Age

Figure 4. von Bertalanffy plots for male and female walleye from North Wabasca Lake, Alberta, 2006. Males: n = 31, L∞ = 460.6, k = 0.350; females: n = 55, L∞ = 603.8, k = 0.220.

4.2 Northern pike

Northern pike accounted for 19.2% of the total catch (158 of 822 fish captured). TCUE was 9.06 fish/100 m2/24 h. Mean CPUE ranged from 6.83 ± 3.50 fish/100 m2/24 h (n = 7) in the 5 to 15 m depth interval to 10.88 ± 3.52 fish/100 m2/24 h (n = 9) in the 0 to 5 m interval. The grand mean CPUE was 9.10 ± 2.45 fish/100 m2/24 h (n = 16).

The proportion of mature northern pike in each age and length class is shown in Tables 4 and 5. While sample sizes of each age class were insufficient to determine the point of 50% maturity, the data showed this occurs earlier than age‐5 for both males and females. The data also showed that 50% of male northern pike are mature before they reach 630 mm TL. Small sample sizes of females in each length category were insufficient to determine the point of 50% maturity.

11 Table 4. Proportion of mature northern pike in each length class captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Total length Males Females (mm) % mature n % mature n 400 ‐ ‐ ‐ ‐ 420 100 1 0 1 440 100 2 100 1 460 100 5 100 3 480 100 3 80 5 500 100 4 100 1 520 67 6 100 2 540 ‐ ‐ 33 3 560 100 2 100 5 580 100 2 100 2 600 100 4 100 8 620 100 3 100 5 640 ‐ ‐ 100 12 660 100 4 100 2 680 100 2 100 5 700 100 1 100 12 720 100 2 100 5 740 ‐ ‐ 100 10 760 ‐ ‐ 100 10 780 ‐ ‐ 100 2 800 ‐ ‐ 100 5 820 ‐ ‐ 100 7 840 ‐ ‐ 100 2 860 ‐ ‐ 100 4 880 ‐ ‐ 100 3 900 ‐ ‐ 100 2 920 ‐ ‐ ‐ ‐

12 Table 5. Proportion of mature northern pike in each age class captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Age Males Females (y) % mature n % mature n 2 ‐ ‐ ‐ ‐ 3 100 1 0 2 4 100 15 94 17 5 75 8 95 19 6 100 5 100 15 7 100 3 100 25 8 100 1 100 21 9 100 3 100 7 10 ‐ ‐ 100 2 11 100 2 100 6 12 100 1 ‐ ‐ 13 ‐ ‐ ‐ ‐

Of the 158 northern pike sampled where sex could be determined, 74.1% (n = 117) were female and 25.9% (n = 41) were male resulting in a female to male sex ratio of 2.85:1. Total length of females ranged from 438.4 to 912.5 mm with a mean length of 696.5 ± 114.65 mm (n = 117; Figure 5), whereas TL of males ranged from 439.4 to 739.2 mm with a mean length of 566.4 ± 87.09 mm (n = 41; Figure 5).

13 1.00 Females (n = 117) 0.90 Males (n = 41) 0.80 ) 2 0.70

0.60 hours/100m 0.50

0.40 (fish/24

0.30 CPUE 0.20

0.10

0.00 400 440 480 520 560 600 640 680 720 760 800 840 880 920 Predicted Total Length (mm)

Figure 5. Length distributions of male and female northern pike captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Males ranged in age from 3 to 12 y with a mean age of 5.74 ± 2.27 y (n = 39; Figure 6), whereas females ranged in age from 3 to 11 y with a mean age of 6.59 ± 1.93 y (n = 114; Figure 6). Overall, mean age of the catch was 6.38 ± 2.05 y (n = 153). The age‐7 cohort was the most abundant year‐class for female northern pike, representing 21.9% (n = 25) of all females. Age‐4 males were most abundant, representing 38.5% (n = 15) of all males. Age‐7 females had a mean TL of 725.4 ± 30.69 mm (n =25). Age‐4 males had a mean TL of 486.9 ± 26.99 mm (n = 15). With average total length exceeding the legal harvest size of 63 cm, the age‐7 female cohort was susceptible to angler harvest.

14 2.00 Males (n = 39) ) 2 1.50 Females (n = 114)

1.00 hours/100m CPUE

0.50 (fish/24

0.00 2345678910111213

Age

Figure 6. Age distributions of male and female northern pike captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

When fitted to the von Bertalanffy growth function, male northern pike had an L∞ of

773.3 mm TL and a growth coefficient k of 0.249 (n = 39; Figure 7). Females had an L∞ of 1,048.0 mm TL and a growth coefficient k of 0.172 (n = 114; Figure 7).

15 1000

800

600 (mm)

Length 400 Total

200

0 024681012

Age

Figure 7. von Bertalanffy plots for male and female northern pike from North Wabasca Lake, Alberta, 2006. Males: n = 39, L∞ = 773.3, k = 0.249; females: n = 114, L∞ = 1,048.0, k = 0.172.

4.3 Yellow perch

Yellow perch accounted for 5% of the total catch (43 of 822 fish captured). TCUE was 2.47 fish/100 m2/24 h. Mean CPUE ranged from 1.18 ± 1.08 fish/100 m2/24 h (n = 9) in the 0 to 5 m depth strata to 4.06 ± 2.93 fish/100 m2/24 h (n = 7) in the 5 to 15 m strata. The grand mean CPUE was 2.44 ± 2.48 fish/100 m2/24 h (n = 16).

The proportion of mature yellow perch in each age and length class is shown in Tables 6 and 7. While sample sizes of each age class were insufficient to determine the point of 50% maturity, the data showed this may occur earlier than age‐3 for males and age‐6 for females. Sample sizes of males and females in each length category were insufficient to determine the point of 50% maturity.

16 Table 6. Proportion of mature yellow perch in each age class captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Age Males Females (y) % mature n % mature n 1 ‐ ‐ 0 1 2 100 1 ‐ ‐ 3 100 2 0 2 4 100 1 0 1 5 ‐ ‐ ‐ ‐ 6 ‐ ‐ 100 2 7 100 2 100 1 8 ‐ ‐ 100 4 9 100 1 100 2 10 ‐ ‐ ‐ ‐

Table 7. Proportion of mature yellow perch in each length class captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Total length Males Females (mm) % mature n % mature n 80 ‐ ‐ ‐ ‐ 90 ‐ ‐ 0 1 100 100 1 0 6 110 ‐ ‐ ‐ ‐ 120 ‐ ‐ ‐ ‐ 130 100 1 0 1 140 100 3 ‐ ‐ 150 100 1 ‐ ‐ 160 ‐ 0 1 170 ‐ 100 1 180 ‐ ‐ ‐ 190 100 1 0 1 200 100 1 ‐ ‐ 210 100 1 100 3 220 100 1 100 3 230 100 1 100 2 240 100 1 ‐ ‐ 250 ‐ ‐ 100 3 260 ‐ ‐ 100 2 270 ‐ ‐ 100 3 280 ‐ ‐ ‐ ‐

17

Of the 39 yellow perch sampled where sex could be determined, 69.2% (n = 27) were female and 30.8% (n = 12) were male resulting in a female to male sex ratio of 2.25:1. Total length of females ranged from 99.0 to 276.7 mm with a mean length of 197.2 ± 64.9 mm (n = 27; Figure 8), whereas total length of males ranged from 105.3 to 247.2 mm with a mean length of 179.8 ± 46.2 mm (n = 12; Figure 8).

0.50 0.45 Females (n = 27) ) 2 0.40 Males (n =12) 0.35 0.30 hours/100m 0.25 0.20 (fish/24 0.15 0.10 CPUE 0.05 0.00 80 100 120 140 160 180 200 220 240 260 280 Predicted Total Length (mm)

Figure 8. Length distributions of male and female yellow perch captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Males ranged in age from 2 to 9 y with a mean age of 5.00 ± 2.65 y (n = 7; Figure 9), whereas females ranged in age from 1 to 9 y with a mean age of 6.15 ± 2.61 y (n = 13; Figure 9). Overall, mean age of the catch was 5.32 ± 2.85 y (n = 22). The age‐8 cohort was the dominant year‐class for females, while age‐3 and 7 fish dominated the catch for males. Harvest of yellow perch is not regulated based on length; therefore all cohorts were susceptible to angler harvest.

18 0.40 Males (n = 7) ) 2 Females (n = 13) 0.30 hours/100m 0.20 (fish/24

0.10 CPUE

0.00 1234567891011

Age

Figure 9. Age distributions of male and female yellow perch captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

When fitted to the von Bertalanffy growth function yellow perch had an L∞ of 266.5 mm TL and a growth coefficient k of 0.276 (n = 20; Figure 10). Sample sizes were not large enough to fit growth of males and females separately.

19 300

250

200 (mm)

150 Length

Total 100

50

0 0246810 Age Figure 10. von Bertalanffy plots for yellow perch from North Wabasca Lake, Alberta, 2006. n = 20, L∞ = 266.5, k = 0.276.

4.4 Lake whitefish

Lake whitefish accounted for 12.2% of the total catch (100 of 822 fish captured). TCUE was 5.74 fish/100 m2/24 h. Mean CPUE ranged from 4.17 ± 5.24 fish/100 m2/24 h (n = 7) in the 5 to 15 m depth interval to 6.68 ± 4.70 fish/100 m2/24 (n = 9) in the 0 to 5 m interval. The grand mean CPUE was 5.58 ± 3.13 fish/100 m2/24 h (n = 16).

The proportion of mature lake whitefish in each age and length class is shown in Tables 8 and 9. While sample sizes of each age class were insufficient to determine the point of 50% maturity, the data showed this likely occurs earlier than age‐5 for both males and females.

20 Table 8. Proportion of mature lake whitefish in each age class captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Age Males Females (y) % mature n % mature n 1 ‐ ‐ ‐ ‐ 2 0 1 0 2 3 100 1 0 2 4 60 5 75 4 5 67 3 100 3 6 100 3 100 3 7 100 4 100 4 8 100 10 100 3 9 100 4 100 6 10 100 7 100 2 11 100 8 100 2 12 100 2 100 3 13 100 3 100 6 14 100 2 100 3 15 100 2 ‐ ‐ 16 ‐ ‐ ‐ ‐

21 Table 9. Proportion of mature lake whitefish in each length class captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Total length Males Females (mm) % mature n % mature n 220 ‐ ‐ ‐ ‐ 240 ‐ ‐ 0 1 260 0 1 ‐ ‐ 280 ‐ ‐ 0 1 300 ‐ ‐ 0 2 320 0 1 ‐ ‐ 340 0 1 ‐ ‐ 360 50 2 ‐ ‐ 380 33 3 100 1 400 100 1 75 4 420 100 3 100 2 440 100 3 100 7 460 100 14 100 3 480 100 6 100 4 500 100 12 100 10 520 100 3 100 9 540 100 3 ‐ ‐ 560 ‐ ‐ ‐ ‐

Of the 99 lake whitefish sampled where sex could be determined, 44% (n = 44) were female and 56% (n = 55) were male resulting in a female to male sex ratio of 0.80:1. Total length of females ranged from 257.4 to 534.8 mm with a mean length of 464.4 ± 68.8 mm (n = 44; Figure 11), whereas total length of males ranged from 273.6 to 545.6 mm with a mean length of 469.1 ± 57.1 mm (n = 55; Figure 11).

22 1.00

0.90 Females (n = 44)

0.80 Males (n =55) ) 2 0.70

0.60

0.50 hours/100m CPUE

0.40 0.30 (fish/24 0.20

0.10

0.00 240 280 320 360 400 440 480 520 560 Predicted Total Length (mm)

Figure 11. Length distributions of male and female lake whitefish captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

Males ranged in age from 2 to 15 y with a mean age of 8.75 ± 3.15 y (n = 55; Figure 12), whereas females ranged in age from 2 to 14 y with a mean age of 8.44 ± 3.66 y (n = 43; Figure 12). Overall, mean age of the catch was 8.54 ± 3.43 y (n = 99). The age‐9 and 13 cohorts were the most abundant year classes for female lake whitefish, together representing 27.9% (n = 12) of all females. Age‐8 males were most abundant, representing 23.6 % (n = 13) of all males. Age‐9 and 13 females had mean total lengths of 496.5 ± 9.35 mm (n = 6) and 526.2 ± 6.06 mm (n = 6), respectively. Age‐8 males had a mean TL of 470.8 ± 5.90 mm (n = 13). Harvest of lake whitefish is not regulated based on length, therefore all age cohorts were susceptible to angler and commercial harvest.

23 0.80 Males (n = 55)

) Females (n = 43) 2 0.60

0.40 hours/100m CPUE

0.20 (fish/24

0.00 12345678910111213141516 Age

Figure 12. Age distributions of male and female lake whitefish captured during the 2006 stock assessment at North Wabasca Lake, Alberta.

When fitted to the von Bertalanffy growth function, male lake whitefish had an L∞ of

527.3 mm TL and a growth coefficient k of 0.300 (n = 55; Figure 13). Females had an L∞ of 526.9 mm TL and a growth coefficient k of 0.326 (n = 43; Figure 13).

24 600

500

400 (mm)

300 Length

Total 200

100

0 0246810121416

Age

Figure 13. von Bertalanffy plots for male and female lake whitefish from North Wabasca Lake, Alberta, 2006. Males: n = 55, L∞ = 527.3, k = 0.300; females: n = 43, L∞ = 526.9, k = 0.326.

4.5 Summary

The data on the status of sport fish in North Wabasca Lake presented in this report will allow fisheries managers to evaluate potential impacts of changing angler pressure on sport fish in North Wabasca Lake, Alberta.

25 5.0 LITERATURE CITED

Berry D.K. 1995. Alberta’s walleye management and recovery plan. Alberta Environmental Protection, Natural Resources Service, Number T/310, , 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.

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, Alberta. 113 pp. von Bertalanffy, L. 1938. A quantitative theory of organic growth. Human Biology 10: 181-213.

26 6.0 APPENDIX

Appendix 1. Universal transverse mercator (UTM) coordinates (NAD 83, UTM zone 11 and zone 12) of test‐netting locations on North Wabasca Lake, Alberta 2006.

Depth strata UTM UTM (m) Site Id Easting Northing 0 to 5 S7a 694721 6221132 S9a 695977 6222987 S10a 693124 6224838 S13a 692089 6209617 S14a 694575 6219030 S1b 316963 6222346 S3b 315227 6216768 S5b 315114 6211003 S11b 319739 6212956

5 to 15 D1a 694230 6221424 D2a 689124 6213685 D6a 692824 6219502 D8a 692275 6215828 D10a 690715 6212269 D5b 319301 6222548 D9b 318587 6213424 a indicates sites in UTM zone 11. b indicates sites in UTM zone 12.

27 Appendix 2. Test netting field data collection sheet.

Lake Monitoring Testing Netting Data Sheet

Waterbody UTM Name: ______Site Id: ______Easting: ______

Date UTM Date Set: ______Pulled: ______Northing: ______

Time Depth Time Set: ______Pulled: ______(m) min: ______max: ______Water Temp: ______

Sample Mesh Fork Length Total Length Weight # Size Species (mm) (mm) (g) Sex Maturity Notes

28 CCONSERVATIONONSERVATION RREPORTEPORT SSERIESERIES The Alberta Conservation Association acknowledges the following partner for their generous support of this project