Year-class component, growth, and movement of juvenile red drum stocked seasonally in a South Carolina estuary

Red drum Sciaenops ocellatus have been classified by the Atlantic States Marine Fisheries Commission as overfished in the Atlantic off the southeastern USA. A study was conducted to evaluate stocking hatchery-reared fish as a management tool to increase abundance of red drum in South Carolina estuaries. Multiple groups of juveniles, at mean sizes of 22-56 mm total length, were released after being marked by immersion in 15 g/L salinity brackish water containing oxytetracycline HCl (500 mg/L active). Fish were released into a small (535-ha) part of the available nursery habitat (total = 25,000 ha) in the Port Royal Sound estuary each fall and spring from fall 1995 through spring 1997. During fall 1995 and spring 1996, 347,000 fish were stocked; during fall 1996 and spring 1997, the number was 1,228,000. Movement of hatchery fish from the release site was monitored for at least 2 years after release. Overall, hatchery fish accounted for 19.0% of the 627 fish (age 0 to age 2) captured from the 1995 year-class and 19.4% of the 687 fish (age 0 to age 2) captured from the 1996 year-class. The portion of each year-class that was of hatchery origin was greatest at the release site (1995 year-class = 58.6%; 1996 year-class = 77.3%). However, marked hatchery fish from the 1996 year-class (range, 8-38%) were also captured after more than 2 years at large and as far as 35 km from the release site. The presence of hatchery fish did not appear to reduce the growth of wild fish even at the higher stocking density tested (2,295 fish/ha). Sex ratios of hatchery and wild fish were not significantly different. Hatchery fish released in the fall were captured 1.5 times more often than fish released in the spring. Additional studies are necessary to determine whether hatchery releases can be used to increase overall abundance.