Year-Class Abundance, Population, and Production of Walleye (Stizostedion vitreum vitreum) in Clear Lake, Iowa, 1948–74, with Varied Fry Stocking Rates

Abstract

Year-class abundance of walleye, Stizostedion vitreum vitreum, in Clear Lake from 1948 to 1974 was significantly correlated (r = 0.613) with annual fry stocking, which was varied from 0 to 6070 fry/ha. Abundance of young walleye seined along shore was even more highly correlated with fry stocking (r = 0.819) but not significantly correlated with year-class abundance (r = 0.179) indicating that year-class strength may change between the first summer and later years. No correlation was found between year-class abundance and temperature in summed degree-days, water levels, or abundance of yellow perch, Perca flavescens, as effects were probably masked by the fry stocking. Growth of age 0 and I walleye were negatively correlated with fry stocking (r = −0.42 and r = −0.41, respectively), but growth of age V walleye was positively correlated (r = 0.70). Growth was also correlated with water levels (r = 0.79). Annual mortality rate averaged 42%. Standing crop ranged from 2.63 to 16.52 kg/ha and annual production from 1.01 to 9.31 kg/ha. Production per biomass was low when water levels were low. Key words: Percidae, walleye, Stizostedion vitreum vitreum, population dynamics, productions, Clear Lake, Iowa, stocking