Dissolved oxygen, temperature and salinity effects on the ecophysiology and survival of juvenile Atlantic sturgeon in estuarine waters: I. Laboratory results

Dissolved oxygen and salinity are relevant structuring factors which should be incorporated into habitat and bioenergetic models for estuarine fishes. We measured growth, food consumption, routine and postprandial metabolism, egestion and survival responses of juvenile Atlantic sturgeon (young-of-the-year: YOY, 6–48 g) in an incomplete factorial array of temperature, salinity and dissolved oxygen levels. Complementary measures were also conducted on yearlings (1 year-old, 70–300 g) to evaluate size and age effects upon food consumption and growth. All three factors had a significant effect on major bioenergetic responses, as well as several of their first order interactions. Maximum growth and food consumption rates were observed above 70% dissolved oxygen saturation, at 20 °C, and between salinities of 8 and 15. Postprandial metabolism was reduced and egestion increased under hypoxia (50% DO saturation), suggesting compensatory mechanisms aimed to reduce assimilation rates. A significant shift in growth responses with age indicated higher tolerance to salinity in yearlings than in YOY. No other size dependent changes were significant, either for hypoxia or for temperature effects. Survival tended to increase with dissolved oxygen saturation, and decreased at the highest temperature and salinity levels. Our results indicated both additive and synergistic effects of tested environmental factors upon ecophysiological responses and highlighted the need to consider these in new bioenergetic models.