Population Structure and Growth of Walleye in Elinor, Haig, Ironwood, and Wadlin Lakes, Alberta, 2008
Author(s)
Shane Wood
Summary
Walleye (Sander vitreus) populations throughout Alberta are faced with high angling pressure, late-maturity and slow-growth rates, resulting in many populations being susceptible to exploitation. In 1995, Alberta Sustainable Resource Development (ASRD) implemented the Alberta Walleye Management and Recovery Plan (AWMRP) to facilitate the protection and recovery of exploited walleye fisheries. As part of the AWMRP, I conducted gill net surveys in four lakes (Elinor, Ironwood, Haig and Wadlin) from 13 to 26 September 2008 to examine population structure and growth of walleye.
Elinor Lake showed a moderate density of walleye, with an estimated mean catch rate of 18.7 walleye/100m2/24 h. Sizes of fish in the population ranged from 109 - 624 mm fork length (FL), but very few fish were > 500 mm FL (the AWMRP standard size). Age ranged from young-of-the-year (YOY) to age 15 fish, but older fish (> age 11) were poorly represented. The population exhibited slow growth with females reaching 500 mm FL at ≥ age 10; no males 500 mm FL were captured. Estimated maximum sizes were 457.6 and 473.1 mm for males and females, respectively, suggesting that walleye in Elinor Lake are unlikely to attain the 500 mm FL standard size. Both sexes appear to mature at a young age, with males reaching maturity by age 4 and females by age 7. Based on AWMRP criteria, the walleye population in Elinor Lake exhibits a wide (> 8 year-classes) and stable (mean age = 6 to 9 y) age-class distribution.
Haig Lake showed a moderately high density of walleye, with an estimated mean catch rate of 21.8 walleye/100m2/24 h. The population exhibited a broad length distribution, ranging from 109 - 675 mm FL with dominant peaks within the 410 - 540 mm FL range. Similarly, the age-class distribution was broad, ranging from YOY to age 18 with a mean age of 8.1 ± 0.3 y (n = 188). Growth was slow, with both males and females reaching 500 mm FL at ≥ age 9. Females (610 mm FL) attained larger estimated maximum sizes than males (513.1 mm FL); on average, male walleye in Haig Lake barely reach the 500 mm FL standard size. Both sexes appear to mature early, with males reaching maturity by age 4 and females by age 6. Based on AWMRP criteria, the walleye population in Haig Lake exhibits a wide and stable age-class distribution.
Ironwood Lake showed a moderately low density of walleye, with an estimated mean catch rate of 10.4 walleye/100m2/24 h. Size of the population ranged from 80 - 566 mm FL, with strong peaks around the 250 and 400 - 500 mm size ranges; however, very few fish were > 500 mm FL. Age distribution was broad, ranging from YOY to age 20 with a mean age of 6.7 ± 0.4 y (n = 126). Growth was slow with both males (one male only) and females reaching 500 mm FL ≥ age 10. Estimated maximum sizes were 444.3 and 516.4 mm FL for males and females, respectively. Thus, male walleye from Ironwood Lake are unlikely to attain the 500 mm FL standard size, while females barely attain this size. Both sexes appear to mature at a young age, with males reaching maturity by age 4 and females by age 5. Based on AWMRP criteria, the walleye population in Ironwood Lake exhibits a wide and stable age-class distribution.
Wadlin Lake showed a moderately low density of walleye, with an estimated mean catch rate of 10.5 walleye/100m2/24 h. Size of the population ranged from 103 to 653 mm FL, with three peaks around the 180, 280, and 520 mm FL size ranges. Age ranged from age 1 to age 18, but the catch consisted of nine age-classes only; mean age was 9.5 ± 0.5 y (n = 194). The population exhibited slow growth, with both males and females reaching 500 mm FL ≥ age 12. Females attained larger (649.7 mm FL) maximum sizes than males (517.4 mm FL); males barely reach the 500 mm FL standard size. Both sexes reached sexual maturity by age 8. Based on AWMRP criteria, the walleye population in Wadlin Lake exhibits a wide and unstable (mean age = 6 to 10 y) age-class distribution.