Differences in growth, consumption, and metabolism among walleyes from different latitudes

Physiological responses to environmental factors such as temperature can vary between stocks of the same species and may be linked to differences in latitude. To determine whether physiological differences exist among populations of young-of-year walleye Stizostedion vitreum as a function of geographic origin, we compared the metabolic rates, food consumption, relative growth, and conversion efficiency among walleyes from Arkansas, Missouri, Wisconsin, and Alberta, Canada, over a range of temperatures (5–25°C). Few or no differences were observed in metabolic rate (mg O₂ · g⁻¹ · h⁻¹) among populations at the cooler temperatures, but walleyes from the Arkansas River, Arkansas, had higher rates than the northern populations at warmer temperatures. Both Arkansas populations also had greater food consumption rates (g · g⁻¹ · d⁻¹) than the northern populations at 25°C. However, growth (g · g⁻¹ · d⁻¹) was similar among stocks within each temperature. Our experiments indicate that physiological differences exist among walleye populations related to latitude. Walleye stocks are adapted to regional thermal conditions, and bioenergetic demands should be taken into account when managing native and introduced populations.