Ecophysiological performance of hatchery-produced red drum (Sciaenops ocellatus) in culture ponds and in Texas coastal waters

Release of hatchery-produced fish to help restore marine fish stocks has been used as a fisheries-management tool for more than 100 years in the United States. The purpose of this research was to improve the understanding of red drum (Sciaenops ocellatus) ecophysiology, as a step toward optimizing performance of juvenile fish released for stock enhancement into Texas bays. Objectives were to (1) assess size variability in hatchery-produced red drum; (2) evaluate abiotic factors that influence their growth, and compare observed growth with predictions generated by the simulation model Ecophys. Fish; and, (3) examine short-term fate of released hatchery fish. Enclosure trials were conducted in hatchery ponds, in the cooling reservoir of an electric power station, and in Corpus Christi Bay. Abiotic environment was monitored near the enclosures. Some pond and field trials compared subhabitat sites expected to provide relatively more and less favorable conditions for red drum growth. Post-release performance of hatchery fish was evaluated by recapturing the fish with a beam trawl as they dispersed into the estuary. Hatchery-produced red drum tolerated a broad range of physicochemical conditions. Fish age and water temperature were the best statistical correlates of growth and size variation. During trials lasting 13 to 32 days, mean survival of caged fish was 65%, and survival rates were similar between subhabitats. Mean length-specific growth rate of caged red drum was about 8% d−1 greater in “good” subhabitat. Ecophys. Fish capably accounted for the observed trends in growth, with upwards of 70% of the variance in observed weight-change rate explained by the model. Hatchery fish released into the wild were recovered in highest densities from seagrass habitats, at distances up to 1.8 km from the release site. Fish began feeding on natural prey within 2–7 days of release, depending on prior conditioning and size. Crude length growth rates of recaptured hatchery fish (0.4 mm d −1) were similar to those reported for wild red drum (0.5 mm d−1) in estuaries. Although dispersal and mortality of released fish were confounded, the recovery data gave no indication of systematic failure by hatchery-produced red drum to survive release into the wild and adapt to natural conditions in a Texas estuary.