Weight-Length Relationships, Approximate Body Composition and Survival of StockedWalleye Fingerlings

摘要

Walleye fingerlings Stizostedion vitreum from stocks having different weight-length relationships were evaluated to determine how these relationships reflect proximate body composition, and how length and body composition influence winter survival. In three successive years (1987-89), fingerlings from two nursey stocks were sampled and released together in two drainable ponds without predators and in a lake with large predators. Weight-length regressions showed that the plumper of the paired stocks were, on average, 7 to 13 percent heavier at length. The plumper stocks survived better over winter in five of six pond trials and in all three lake trials. Disease, however, was a factor in fall 1988. The plumper stocks significantly exceeded the lighter stocks in mean length by 15 mm in 1987 and 8 mm in 1989, however, fish length did not appear to an important factor limiting survival. Elevations of fish weight-length regressions lines increased over winter. Mortality of lighter fish could not be ruled out as a contributing factor, however, in four of the stocks, winter weight gains by undetermined numbers of walleye in the ponds were indicated by increases in numbers of positive residuals when spring weight-length coordinates were compared with fall regression lines.