Relationships between Relative Weight, Prey Availability, and Growth of Walleyes in Oneida Lake, New York

Abstract

Assessment of predator–prey dynamics is a central feature of community-based fisheries management, and a variety of fish condition indices have been developed from length–weight data to make inferences about feeding conditions. Relative weight (W_r ) is useful for measuring fish condition, is easily calculated, and has simple data requirements; however, few studies have empirically validated W_r indices. We compared the W_r of walleyes Sander vitreus in Oneida Lake, New York, with prey fish availability and walleye growth observed over 23 years (1961–1983). For each year, we calculated the W_r for three length-classes (350, 400, and 450 mm total length) of walleyes caught in October. Prey fish availability was calculated from annual estimates of (1) prey biomass in bottom trawl catch and (2) biomass of age-3 and older walleyes estimated from mark–recapture studies. Growth of walleyes (ages 4–6) was determined using lengths at age that were back-calculated from scale annuli. The W_r declined as walleye length-class increased, and W_r was positively related to both prey fish availability and walleye growth. Our study suggests that W_r can be a useful tool for describing feeding conditions and assessing predator–prey relations.