Use of Allozyme Markers to Evaluate Walleye Stocking Success

Abstract

An unbiased assessment of the relative success of stocking walleye Stizostedion vitreum at different sizes can be accomplished only when comparisons are made simultaneously in the same lake. Previously, these comparisons had not been made because small fish could not be tagged effectively. Electrophoretically detectable allozyme polymorphisms, however, can be used as “genetic tags,” and thus large numbers of fish with permanent, heritable, selectively neutral markers can be produced. During 1987 and 1989 we used two alleles at the IDHP-1* locus to genetically tag three groups of walleyes, each with one of three distinct genotypes. Three size-groups of fish were stocked into each of several small northern Illinois impoundments as follows: fry at 2,500/hectare, 50-mm fingerlings at 125/hectare, and 100-mm fingerlings at 60/hectare. We quantified the relative success of each stocking strategy by sampling surviving walleyes by electrofishing, then assigning individuals to test groups through electrophoretic analysis of fin tissue. Relative stocking success among test groups was highly variable, both among lakes and between years. In addition, although fry and 50-mm fingerlings had better first-year growth than did 100-mm fingerlings during 1987, this trend was not observed in 1989. Finally, zooplankton abundance at the time of fry stocking was positively correlated with relative success of walleyes that were stocked as fry.