Geographical range of a species can be limited by environmental conditions such as temperature. This is important to understand when trying to establish a new fish population on the fringe of their range. The Oklahoma Department of Wildlife Conservation (ODWC) has been stocking tiger muskellunge (Esox masquinongy x E. lucius) in Lake Carl Etling in northwestern Oklahoma since 2014 with little success. This reservoir experiences a broad range of temperatures that could affect recruitment of tiger muskellunge, especially during times of the year when prey are not abundant. To explore the possible effects of temperature and prey availability on post-stocking survival, temperature tolerances of juvenile tiger muskellunge were determined in laboratory trials using starved and fed fish (n=9 each) acclimated to temperatures of 20, 24, and 28°C. We used the lethal thermal maxima (LTM) procedure to determine the upper thermal tolerances of starved and fed tiger muskellunge subjected to a 1°C h-1 increase. Response variables consisted of three sub-lethal responses (initial loss of equilibrium, final loss of equilibrium, loss of motion) and the temperature at which death occurred. The temperature at which final loss of equilibrium, loss of motion, and death occurred generally increased with acclimation temperature for fed fish but decreased with acclimation temperature for starved fish. At 20°C acclimation, no difference was observed between fed and starved fish, but the feeding treatments were always significantly different at the 28°C acclimation temperature. Starvation lowered the thermal tolerance of juvenile tiger muskellunge, which could negatively affect stocking success if stocked fish do not have access to ample vulnerable forage as reservoir water temperatures increase seasonally.
