Meeting Abstract
Hatchery production and stocking are essential to the restoration of endemic lake sturgeon populations, but environmental factors can limit survival both in the hatchery and after release into the river system. This study investigated the effects of ambient temperature on the energy physiology of hatchery-reared lake sturgeon. Immediately after first feeding, juvenile fish were exposed to three temperatures (15, 18, and 21°C) for six weeks. Surprisingly, no differences in growth were observed between treatments, although sturgeon reared at 15°C exhibited significantly higher survival. Sampled fish were subsequently analyzed for whole-body triglyceride, glucose, and protein concentrations to examine any temperature-dependent differences in production of energy reserves in the early life stages. Lean muscle production was prioritized in the initial months of life at all tested temperatures, with protein concentrations accounting for the greatest proportion of body mass in fish exposed to 15°C. These results indicate that temperature is an important factor affecting the trade-off between rapid growth and nutritional condition of juvenile lake sturgeon. After 6 weeks, all remaining fish were transferred to 20°C and reared to stocking size (10.1±0.5 g). Standard metabolic rate (SMR) was determined for each treatment group via intermittent-flow respirometry at the three rearing temperatures. As expected, SMR increased with temperature in all treatment groups. However, lake sturgeon fingerlings initially reared at 18°C exhibited greater range in SMR across exposure temperatures. Thus, temperatures experienced in early life influence the physiological condition of lake sturgeon, and these impacts continue to influence physiological tolerance to temperature variation over the course of development to stocking size.
