CONTRIBUTION AND MOVEMENT OF HATCHERY-PRODUCED RED DRUM Sciaenops ocellatus STOCKED IN TWO SOUTH CAROLINA ESTUARIES

The South Carolina Department of Natural Resources has been stocking red drum (Sciaenops ocellatus) into local estuaries since 1988 to evaluate estuarine-specific recruitment dynamics and supplement local populations. Multiple genetically-identifiable groups of hatchery-produced red drum were stocked into two South Carolina estuaries, Murrells Inlet and Winyah Bay, during 2005-2009.  Release treatments included small juveniles (20-40 mm TL) stocked in both estuaries at approximately 30 days post hatch and medium juveniles (120-160 mm TL) stocked in Murrells Inlet at approximately 200 days post hatch.  Red drum samples were collected post stocking via fisheries independent and dependent sampling and evaluated by microsatellite-based parentage analysis to determine hatchery contribution and dispersal of hatchery fish from stocking locations.

Table 1.  Number stocked and contribution of hatchery red drum in Murrells Inlet and Winyah Bay, 2005-2009.

Small juvenile red drum stocked in relatively low densities (27-83 fish/ha) in Winyah Bay made contributions (13.0-35.3%) in each year of stocking.  Small juveniles stocked at high densities (186-1,912 fish/ha) made negligible contributions in Murrells Inlet (0-3.4%), while medium juveniles stocked in lower densities (5-24 fish/ha) made contributions of 19.2-79.5%.  The results suggest that physical characteristics of the Murrells Inlet estuary limit the survival of fish stocked at a small size.  Fish held and released the following spring appear to bypass those limitations and make strong contributions to the local red drum population, even when stocked in relatively small numbers.  Red drum stocked in Winyah Bay were recovered in Murrells Inlet and red drum stocked in Murrells Inlet were recovered in Winyah Bay, despite the unconnected nature of the two estuaries.  The study results suggest that 1). A well-designed stocking plan should account for the limitations of the receiving estuary in order to determine the proper size at stocking and 2.) Hatchery red drum released at small sizes may be more mobile than previously believed.