Evaluating a Three-Fold Continuum of Fry Stocking Density for Rearing Walleye in Lined Ponds

Abstract

Fry stocking density can affect harvest metrics for fingerling walleye (Stizostedion vitreum) reared in drainable ponds, but few studies have examined these relationships with the use of elevated walleye fry stocking densities in lined ponds. Correlation and regression analyses were used to assess how a three-fold change in walleye fry stocking density (234,375 to 703,125 per hectare) relates to harvest metrics and length of the culture period, as well as the tradeoff experienced between walleye size (grams) and harvest density in 0.32hectare lined ponds over a nine-year period at Blue Dog State Fish Hatchery, South Dakota. As fry stocking density increased, so did harvest metrics for both number (r = 0.85, P < 0.01) and yield (r = 0.81, P < 0.01). Length of the culture period varied between 24 and 35 days and was negatively related to stocking density (r = −0.66, P < 0.01). The linear relationship between harvest density and yield was highly correlated (r = 0.95, P < 0.01) with highest values measuring 617,625 walleye and 173 kilograms per hectare. Harvest density explained 61% of the variation in walleye size (P < 0.01) and exhibited a decreasing curvilinear relationship such that continued increases in harvest density resulted in smaller reductions in fish size. Increasing fry stocking density from 234,375 to 703,125 per hectare in lined ponds coincided with increased rearing efficiencies for number and yield, as well as a reduced culture period. Minimal reduction in walleye size occurred once harvest density exceeded 300,000 per hectare.