LAUSR

In many fish species, ontogenetic dietary shifts cause changes in both quantitative and qualitative intake of energy, and these transitions can act as significant bottlenecks in survival within a given year class. In the present study, we estimated routine metabolic rate (RMR) and forced maximum metabolic rate (FMR) in age 0 lake sturgeon (Acipenser fulvescens) on a weekly basis from 6 to 76 days posthatch (dph) within the same cohort of fish. We were particularly interested in the period of dietary transition from yolk to exogenous feeding between 6 and 17 dph and as the fish transitioned from an artemia-based diet to a predominantly bloodworm diet between 49 and 67 dph. Measurement of growth rate and energy density throughout indicated that there was a brief period of growth arrest during the transition from artemia to bloodworm. The highest mass-specific RMR (mg O2 kg−1 h−1) recorded throughout the first 76 d of development occurred during the yolk sac phase and during transition from artemia to bloodworm. Similarly, diet transition from artemia to bloodworm—when growth arrest was observed—increased scaled RMR (i.e., mg O2 kg−0.89 h−1), and it did not significantly differ from scaled FMR. Log-log relationships between non-mass-specific RMR or FMR (i.e., mg O2 h−1) and body mass significantly changed as the growing fish adapted to the nutritional differences of their primary diet. We demonstrate that dietary change during early ontogeny has consequences for growth that may reflect altered metabolic performance. Results have implications for understanding cohort and population dynamics during early life and effective management for conservation fish hatcheries.