Behavioral condition of red drum Sciaenops ocellatus fingerlings exposed to habitat structures and predators in rearing ponds

Stock enhancement programs strive to propagate fish similar to their wild counterparts, but hatchery-reared fish are often deficient in their ability to detect and avoid predation. The objective of this study was to determine if the provision of complexly structured habitat would improve post-stocking survival of hatchery-reared red drum, Sciaenops ocellatus, when exposed to free-roaming predators. Experiments were conducted in 0.2 ha rearing ponds between July and December 2016 at the Coastal Conservation Association Marine Development Center in Corpus Christi, Texas. Three habitat treatments (non-vegetated [normal rearing], artificial seagrass, and artificial seagrass with predator exclusion cages) were used to assess if habitat complexity influenced growth and condition. Fish growth (TL) was affected by trial (i.e., seasonality; P < 0.0001) but not by treatment (P = 0.178). After rearing to the fingerling stage (36 days post-hatch), survival from predation was assessed by exposing red drum to free-roaming predators (pinfish, Lagodon rhomboides) in experimental “wild” ponds (0.2 ha) with artificial seagrass for 24 hours. In two trials, fish condition (K) differed significantly among treatments (P<0.0001) and was lower in the artificial seagrass treatment with predator exclusion cages compared to the other treatments. Red drum may have been more active and vigilant (“leaner”) when exposed to caged predators, while the fish in the unstructured habitat led a more sedentary life (“fat”). Overall, when exposed to free-roaming predators in a “wild simulation” fish reared in ponds with the addition of structured, complex habitat survived better. The results of this study suggest that the provision of complexly structured habitat improved behavioral mechanisms (i.e., foraging, predator-avoidance) that may increase post-release survival of hatchery-reared red drum.