Development and utilization of a population growth history of Red Lake walleye, Stizostedion vitreum

Synopsis An environmental growth history of commercially harvested walleye, Stizostedion vitreum, in Red Lakes, Minnesota, was constructed for the years 1944–1992. This was accomplished using a linear model which was fitted to annular scale increment measurements. Increment size was separated into one component due to a combination of environmental factors, an environmental growth coefficient, and one due to the age of the fish. Our hypothesis was that variables such as air temperature, walleye year-class strength, catch-per-unit-effort (CPUE) of walleye, and CPUE of yellow perch, Perca flavescens, affect walleye growth, and therefore a historical series of these variables would show coherence to the series of walleye growth coefficients. Multiple regression techniques were used to test these hypotheses. Significant predictors of the growth of walleye after age one were average February temperature, cumulative degree days in July, walleye year-class strength, and growth of young-of-the-year (YOY) walleye. We hypothesized that YOY walleye respond to a different set of factors than walleye after age one, thus, a series of YOY growth measurements would show coherence to a different set of environmental factors. Significant predictors of YOY walleye growth were May, June, and August cumulative degree days, as well as the growth of older walleye. We expected the set of factors which affect freshwater drum, Aplodinotus grunniens, to include factors that affect walleye, such as temperature, shared prey availability, and abundance of both walleye and drum. As a test, environmental growth coefficients computed by Pereira (1992) for freshwater drum were compared to walleye growth coefficients. The growth coefficients of drum were significantly positively correlated with the walleye coefficients, and the significance increased if the poorest walleye growth years were excluded.