The Effect of Habitat Exposure and Ontogeny on the Survival Skills of Hatchery Red Drum

Abstract

We examined the influence of prerelease exposure to natural vegetation on the survival skills of a marine finfish, the red drum Sciaenops ocellatus. Red drum larvae at 18 d posthatch (10–12 mm standard length [SL]) were collected from a Texas Parks and Wildlife Department hatchery and reared with and without smooth cordgrass Spartina alterniflora, for either 10 or 20 d. High-speed video was then used to quantify a suite of prey capture and antipredator performance variables at days 28 (∼23 mm SL) and 38 (∼32 mm SL). Repeated-measures analysis of variance indicated that the timing and distance of key variables (e.g., maximum gape, time to maximum gape, gape cycle duration) increased significantly in older fish, while reaction distance and time to maximum velocity decreased with age. The time to reach maximum velocity was less for individuals reared in vegetation, yet these fish also had a shorter reaction distance to predatory stimuli and took longer to capture prey. Additionally, interindividual variability (as measured by the coefficient of variation) ranged from 0.0% to 101.3% and from 3.4% to 110.1% for the prey capture and antipredator variables, respectively, indicating that performance varied substantially among individuals. Our results indicate that while prerelease exposure to smooth cordgrass habitat does not afford any obvious survival benefits to red drum, ontogeny appears to have a direct effect on the development of key survival skills in this species.