Effects of walleye stocking on year-class strength

The success of stocking program involving walleye Stizostedion vitreum has frequently been judged by the contributions of the stocked walleye to the abundance of year-classes. But evaluation methods based only on contributions to the year-class augmented may be biased. We developed a method of estimating walleye year-class strength based on catch-at age data from routine fish population assessments. We then examined the effect of walleye stocking on the stocked year-class and other year-classes by using catch-at- age data from walleyes in 200 Minnesota lakes. Although stocking increased the abundance of a year class in lakes with natural walleye reproduction, stocking, especially of fingerlings, decreased the abundance of year-classes 1 year younger and 1 year older than the stocked year class. In lakes without natural walleye reproduction, stocking did not affect adjacent year-classes significantly.