Effects of Thermal Incubation Regimes on Larval Lake Sturgeon Development and Behavior

Climate change and variability are affecting thermal regimes in aquatic systems worldwide. Understanding how variation in temperature affects ontogenetic development is a major goal for researchers and managers. The early life stages of aquatic ectotherms are particularly susceptible to environmental variability given that streams are important integrators of climatic features. Using lake sturgeon (Acipenser fulvescens) from Black Lake, MI, we reared eggs from ten half-sibling families under four thermal regimes: two constant (10 and 18C) and two fluctuating (10-19C) treatments representing mean, ambient, and the highly variable effects of dam impoundment on diel variation in water temperature. Individuals were photographed at hatch to quantify phenotypic traits, placed in individual incubation chambers, and monitored until the timing of larval emergence. Repeated measures of phenotypic traits at emergence were used to estimate growth. Larval traits at hatch varied significantly among families within the four treatments due to genotype-by-environment interactions and the largest range of phenotypic variation was observed in the constant 18C treatment. Family (additive variance) and treatment (environmental) effects were also associated with emergence time and growth. Results indicate that thermal conditions experienced during early ontogenetic stages can alter population phenotypic and genotypic distributions.