Stocking South Carolina's Favorite Saltwater Fish
The South Carolina angler’s favorite saltwater fish has many names: red drum, redfish, spottail, channel bass.
Fluctuations in the population of this favored fish are often addressed by fisheries managers who make adjustments to the slot sizes and the number of fish that anglers can bring home. Currently in South Carolina, the slot size for red drum is 15-23 inches in length and the bag limit is 3 fish per person per day.
Another tool the South Carolina Department of Natural Resources (SCDNR) uses to help manage red drum is a marine fish stocking program, which produces about 1.5 million spottails annually to stock, or release, into South Carolina waters to help support the wild population. South Carolina is one of the only states with this kind of program.
There are a lot of moving parts to a stock enhancement program, from collecting adults to releasing young fish to determining their survival.
SCDNR’s red drum stocking program starts with locally caught adults that reflect the same genetics found in the wild fish population. As many as 50 mature, 25-lb fish can live in large tanks at SCDNR’s Marine Resources Research Institute in Charleston. These parent fish are treated like royalty, served all the shrimp, squid and fish they can eat. Temperature and day length are two cues that cause red drum to spawn in the fall – so in the lab, tanks are heated and cooled and light levels are changed to simulate the seasons just as the fish would experience in the wild.
The adult females lay millions of eggs that soon hatch into larvae. These tiny fish, just a tenth of an inch long, are then collected and transported to SCDNR’s Waddell Mariculture Center in Bluffton, where they are placed in large saltwater ponds. The ponds provide a perfect environment with no predators and lots of larval fish food (small crustaceans). The red drum larvae grow extremely fast – in just 30 days, they will be one-inch-long and ready to be released into one of the estuaries up and down the South Carolina coast.
After many years of experimentation, SCDNR scientists have learned the best size of fish to stock, the best season in which to release them, and the best tags for identifying the fish years later. That way, SCDNR biologists can determine just how successful the program is in increasing spottails in the wild. All of this experience suggests that one-inch fish survive best when released during the same time of year (September-October) that they would be that size in the wild (apparently Mother Nature knows best).
So how do you tag a one-inch fish? All of the fish released by the stocking program are identifiable by their DNA. If you know the genetics of the parents, then you know the genetics of all of their offspring – and later on, when fish are sampled from the wild, genetic testing makes it possible for biologists to determine which is a wild fish and which is a stocked fish.
In recent years, SCDNR has stocked fish in the Colleton River, Broad River, ACE Basin, North Edisto, Charleston Harbor, Winyah Bay, Murrells Inlet and Cherry Grove. In some estuaries such as Winyah Bay, as many as 25% of the fish caught were released as part of the stocking program, ensuring that there are fish available for anglers to catch.
About the author: Mike Denson is the director of SCDNR’s Marine Resources Research Institute, where he has worked as a scientist in the mariculture section for over 20 years.