Effects of Temperature and Feed Energy on the Performance of Juvenile Red Drum

• Published in: Transactions of the American Fisheries Society
• Main Authors: Fontaine, Lance P., Whiteman, Kasey W., Li, Peng, Burr, Gary S., Webb, Kenneth A., Goff, Jonathan, Gatlin, Delbert M., Neill, William H., Davis, Kenneth B., Vega, Robert R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Red drum; Sciaenops ocellatus
• Online Access: http://dx.doi.org/10.1577/t06-136.1; https://afspubs.onlinelibrary.wiley.com/doi/pdf/10.1577/T06-136.1

Abstract We tested the hypothesis that the growth of fish exposed to high temperatures can be limited by available food energy whereas that of fish exposed to low temperatures can be limited by their metabolic capacity to exploit the available food energy. Under laboratory conditions we evaluated growth (%/d) and marginal metabolic scope (MMS; L·g −1 ·h −1 ) of juvenile red drum Sciaenops ocellatus exposed to two levels of dietary energy, low (LE; ∼4.1 kJ/g) and high (HE; ∼15.9 kJ/g), and to three temperatures, approximately 19, 25, and 29°C, for a period of 6 weeks. Growth rate and MMS increased with temperature, but only growth rate increased with dietary energy and then only at the higher two temperatures. The simulation model Ecophys. Fish was employed to elucidate experimental results potentially confounded by interactions between fish weight and the controlling effects of temperature on metabolism. The simulated and observed results both showed that performance is enhanced at higher temperatures, especially for fish consuming the HE diet. A subsequent 6‐week‐long experiment confirmed results for fish fed the two diets at ambient temperature (∼26°C) and sought to further resolve responses by examining body condition indices and proximate composition. Additionally, these fish were assayed for differential cortisol response to 15 min of confinement stress. The feed efficiency, hepatosomatic index, intraperitoneal fat ratio, and whole‐body fat of fish fed the LE diet were significantly lower than those of fish fed the HE diet, indicating relative energy malnutrition in the LE group. As with MMS, no apparent differential effect of feed energy on the pre‐ or poststress values of plasma cortisol was observed. These findings support the ideas that red drum obtain greater metabolic capacity when they are exposed to a near‐optimal temperature and that their ability to transform that capacity into growth is maximized only when they are provided a nutritious, high‐energy diet.