Fall Walleye Index Netting at Sturgeon Lake, Alberta, 2007


Author(s)

Nathan Carruthers, Tyler Johns and John Tchir

Summary

Strategies implemented by Alberta Sustainable Resource Development (ASRD) to manage sport fish populations (e.g., sport fish regulations) require ongoing monitoring to evaluate their effectiveness. Our goal was to estimate relative abundance, population structure, and growth of sport fish, primarily walleye (Sander vitreus), in Sturgeon Lake, Alberta. Data were also collected on northern pike (Esox lucius), yellow perch (Perca flavescens) and lake whitefish (Coregonus clupeaformis).

Between 11 and 13 September 2007, we captured a total of 1,338 fish at Sturgeon Lake using the Fall Walleye Index Netting (FWIN) method. Species caught included walleye, northern pike, lake whitefish, yellow perch, white sucker (Catostomus commersoni), spottail shiner (Notropis hudsonius), and trout perch (Percopsis omiscomaycus). Walleye was the most abundant sport fish in the catch and yellow perch the least abundant.

We captured a total of 907 walleye. Total catch-per-unit-effort (TCUE) of walleye was 41.50 fish/100 m2/24 h and mean catch-per-unit-effort (CPUE) for combined depth strata (2 to 5 m and 5 to 10 m) was 41.52 fish/100 m2/24 h (n = 20 nets). Mean CPUE of adult walleye (sexually mature) was 19.83 fish/100 m2/24 h (n = 20 nets). For walleye sampled where sex could be determined, 50.8% were females and 49.2% were males resulting in a female to male sex ratio of 1.03:1. Total length (TL) of females ranged from 110 to 590 mm with a mean (± SD) length of 393.7 ± 83.3 mm, whereas TL of males ranged from 113 to 535 mm with a mean length of 384.4 ± 66.1 mm. Mean age of male walleye (± SD) was 5.85 ± 4.27 y (range = 0 to 24 y) and mean age of female walleye was 4.35 ± 2.69 y (range = 0 to 14 y). For both sexes, age-3 fish dominated the catch of walleye.

We captured a total of 76 northern pike. TCUE of northern pike was 3.48 fish/100 m2/24 h and mean CPUE for combined depth strata was 3.59 fish/100 m2/24 h (n = 20 nets). Mean CPUE of adult northern pike was 3.21 fish/100 m2/24 h (n = 20 nets). For northern pike sampled where age could be determined, 66.7% were females and 33.3% were males resulting in a female to male sex ratio of 2:1. Total length of females ranged from 364 to 1,117 mm with a mean length of 598.9 ± 134.4 mm, whereas TL of males ranged from 358 to 600 mm TL with a mean length of 492.8 ± 74.4 mm. Mean age of male northern pike was 3.29 ± 1.99 y (range = 1 to 8 y), whereas mean age of females was 4.76 ± 2.39 y (range = 1 to 13 y). Age-2 males and age-5 females dominated the catch of northern pike.

We captured a total of 65 yellow perch. TCUE of yellow perch was 2.97 fish/100 m2/24 h and mean CPUE for combined depth strata was 2.99 fish/100 m2/24 h (n = 20 nets). Of yellow perch sampled where sex could be determined, 38.6% were females and 61.4% were males resulting in a female to male sex ratio of 0.63:1. Fork length (FL) of females ranged from 102 to 270 mm with a mean length of 166.4 ± 60.8 mm, whereas FL of males ranged from 106 to 258 mm with a mean length of 139.6 ± 33 mm. Mean age of male yellow perch was 1.57 ± 1.16 y (range = 1 to 5 y), whereas mean age of females was 1.71 ± 1.11 y (range = 1 to 4 y). For both sexes, age-1 individuals dominated the catch of yellow perch.

We captured a total of 142 lake whitefish. TCUE of lake whitefish was 6.36 fish/100 m2/24 h and mean CPUE of combined depth strata was 6.37 fish/100 m2/24 h (n = 20 nets). Mean CPUE of adult lake whitefish was 2.52 fish/100 m2/24 h (n = 20 nets). Of lake whitefish sampled where sex could be determined, 53.6% were females and 46.4% were males resulting in a female to male sex ratio of 1.09:1. FL of females ranged from 209 to 591 mm with a mean length of 384.5 ± 108.1 mm, whereas FL for males ranged from 209 to 526 mm with a mean length of 350.4 ± 107.5 mm.

The results of this study have been used by ASRD to set fishing regulations in Sturgeon Lake for 2008 - 2009.

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