Growth and Survival of Four Sizes of Stocked Largemouth Bass

Abstract

AbstractWe compared growth and survival (including losses to stocking stress and predation) of four sizes of largemouth bass Micropterus salmoides in four Illinois reservoirs. Fish were stocked as small fingerlings (55 mm total length) in July, medium fingerlings (100 mm) in August, large fingerlings (150 mm) in September, and advanced fingerlings (200 mm) the subsequent spring. Survival of small fingerlings was very low (catch per unit effort < 1 fish/h of electrofishing in the fall after stocking), and fish stocked as small fingerlings were not observed in electrofishing samples after the spring following stocking. In samples collected soon after stocking, large and advanced fingerlings were larger and more abundant than other sizes. However, in subsequent sampling, there were no differences in size or survival among fish stocked as medium, large, and advanced fingerlings. Long‐term growth of stocked fish was similar to that of wild fish, but survival of stocked fish was low for all sizes. Mean initial stocking mortality for fish held in cages was variable but generally low (0.0–5.6%) and was related to lake temperature at stocking. The diets of predators (primarily adult largemouth bass) contained high numbers of small‐, medium‐, and large‐sized fingerlings after stocking, but no predation was observed on advanced fingerlings. Cost of producing fish increased with size, and cost–benefit analysis determined that medium (100‐mm) fish had the greatest return per cost. We recommend stocking medium fingerlings because the stocking of larger fingerlings did not produce a significant increase in survival.