The Role of Ciscoes as Prey in the Trophy Growth Potential of Walleyes

Abstract

Abstract Analysis of the growth characteristics of 215 populations of walleye Sander vitreus across Ontario revealed that female walleyes reached larger asymptotic lengths in lakes in which ciscoes Coregonus artedi provided a relatively large prey species for them. The stomach contents of walleyes from a set of intensively studied lakes revealed that walleyes of all sizes depended on ciscoes but that ciscoes were most important to larger walleyes. In lakes without ciscoes, the walleye diet closely tracked the availability of young-of-year yellow perch Perca flavescens; when such prey were in short supply, walleyes consumed invertebrates. The prey size in walleye stomachs was significantly larger in lakes with ciscoes, but the probability of finding empty stomachs was also greater. This suggests that although walleyes in lakes with ciscoes foraged less often, more energy was available for growth. Exceptions to this general pattern occurred when ciscoes were too large to be consumed by walleyes or ciscoes were absent but small prey (i.e., yellow perch) were very abundant. We propose that lakes without ciscoes will provide higher catch rates for anglers, whereas those with ciscoes (particularly small ciscoes) are more likely to provide opportunities for trophy size fish.