Modeling sources of variation for growth and predatory demand of Lake Eriewalleye (Stizostedion vitreum), 1986-1995

Given the variable nature of the Lake Erie ecosystem, we investigated bioti c and abiotic sources of variation for walleye (Stizostedion vitreum) growt h, consumption, and population-wide predatory demand. We determined how tem perature, population structure, and age-specific consumption influenced wal leye growth and consumption during 1986-1995. For each year, we used indivi dual-based bioenergetics modeling to compare growth and consumption by wall eye in Lake Erie's western or central basin with those of walleye moving se asonally between basins. Population structure strongly affected walleye gro wth and consumption but had little influence on interbasin growth rate comp arisons. Based on water temperature alone, growth and consumption by wester n basin walleye were generally lower than for central basin or migratory po pulations and were more limited by summer water temperatures. In simulation s combining effects of population structure, temperature, and age-specific consumption, migratory walleye grew most rapidly, taking advantage of tempe rature-related growth peaks in both basins. Estimates of walleye predatory demand declined with population size from 1988 through 1995. With natural f eedbacks, predatory demand interacts with prey production, limiting walleye reproductive potential when prey availability is low. However, immediate i mpact on predatory inertia is limited, complicating our ability to predict how predatory demand and prey availability interact in Lake Erie.