Effects of rearing temperature on growth, energy reserves, and thermal plasticity of juvenile lake sturgeon.

Hatchery-raised lake sturgeon (Acipenser fulvescens) are essential to the restoration of this species, but deviation from optimal juvenile growth conditions may limit post-stocking survival. This study investigated the effects of temperature for lake sturgeon raised at 15 °C, 18 °C, and 21 °C. Survival, growth, and synthesis and storage of metabolic energy reserves were measured weekly for 6 weeks following the onset of exogenous feeding. No significant differences in survival, total length, body mass, or SGR were observed based on rearing temperature. Whole-body lipid concentrations were stable over 6 weeks of growth, while mass-specific protein concentrations were significantly increased in all treatments starting at week 3, suggesting the prioritization of lean muscle production in early life at all tested temperatures. Furthermore, total protein accounted for a greater proportion of body mass in fish exposed to lower temperatures. Finally, persistent effects of rearing temperature were examined in stocking-size juveniles by measuring standard metabolic rate following acute transfer from 20 °C to each of the initial rearing temperatures. Metabolic rate increased with temperature, with no differences between rearing groups at each of the measured temperatures. However, fish reared at 18 °C demonstrated improved plasticity within the measured temperature range compared to lake sturgeon that experienced low (15 °C) or high (21 °C) temperatures in their early life. These results indicate that temperature plays a role in balancing the trade-off between rapid growth and nutritional condition of juvenile lake sturgeon, and thermal plasticity later in life, which may influence recruitment to depleted populations.