Comparative Gear Selectivity for Male Walleyes and Influence of Method of Capture on Resultant Hatching Success

Abstract

Spawn-taking efforts for walleyes Stizostedion vitreum in Colorado were used to evaluate gear selectivity in terms of catch per unit effort (CPUE) and sex ratio. Seasonal electrofishing CPUE ranged from 28 to 197 walleyes/h, whereas gillnetting CPUE ranged between 0.5 and 3.0 walleyes/net-night. Corresponding sex ratios (male: female) for these gears ranged between 9.5 and 48.3 for electrofishing and 0.3 and 0.5 for gillnetting. Weighted percent hatching success was also determined for eggs fertilized with milt from electrofished males versus gillnetted males to determine if electrofishing harmed male gametes. The weighted percent hatch for electrofishing was 69.1%, compared with 76.9% for gillnetting (P = 0.357). These results suggest that electrofishing may be used to enhance numbers of male broodstock during spawn-taking operations. Electrofishing is an efficient means of capturing male broodstock during spawning season, and the resultant hatching percentage of eggs fertilized with these males is comparable with percentages obtained with gillnetted males.