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January 02, 2006

DNR Stocks Nearly Three Million Red Drum

Biologists released approximately 2.9 million juvenile red drum into four estuaries.

The S.C. Department of Natural Resources (DNR) completed the year's release of red drum into South Carolina's estuaries this fall. Red drum are also known as spottail bass and redfish, and are considered to be the most popular inshore species sought after by anglers in the state.

Biologists released approximately 2.9 million juvenile red drum into four estuaries. These include the Colleton River in Beaufort County, the North Edisto River in Charleston County, and Murrells Inlet and Winyah Bay estuaries in Georgetown County.

Contact DNR biologist Wallace Jenkins at 843-953-9835 or via email at for more information on the program.

"This is the most fish we have ever released in one year and allows us to simultaneously conduct a number of studies," said Jenkins.

For the third year in a row DNR staff were able to increase production by improving management techniques. During this three year period production has increased by nearly 33 percent. "This year we were fortunate to be able to send a staff member to Texas to gain experience producing red drum with the Texas Parks and Wildlife staff at the Sea Center Texas. The methods used in Texas were directly applicable to our activities and allowed us to reduce some of the variability in production that we have encountered in the past," said Jenkins. "In addition, the average size at release was intentionally increased from .75 inches to nearly 1.5 inches, which should greatly increase post release survival of the stocked fish," Jenkins said.

The goal of the project is to determine whether stocking can increase the population of red drum along South Carolina's coast. The Atlantic States Marine Fisheries Commission currently defines the red drum fishery as over-fished. The changes in size and catch limits that were enacted by the South Carolina General Assembly in August 2001 are projected to significantly help the population move to a position of sustainable when the next assessment is completed in 2009.

The DNR collects and spawns wild adults each year to produce the fish to be stocked. The approach mimics the fish's natural cycle by having the red drum spawn, or reproduce, during their regular mating season of August and September. Once the adult red drum spawn in the Charleston lab on James Island, biologists move the larvae to rearing ponds at the DNR's Waddell Mariculture Center in Bluffton where the actual production of juveniles occurs. When the offspring reach the appropriate size they are harvested, marked and released into their natural marsh habitat.

"The primary difference is that the stocked fish are protected from predators for their first month of life compared with their wild counterparts, which enter the estuary near the bottom of the food chain and are more vulnerable to predation and environmental influences," Jenkins said.

"Marking" the fish consists of exposing them to a chemical called oxytetracycline, which binds to their bones and can be viewed under a special microscope. In addition, genetic identification techniques developed by DNR researchers at the Hollings Marine Lab have resulted in all fish being automatically marked during normal hatchery operations. Use of genetic marking techniques allows hatchery fish to be identified by simply removing a tissue sample and not sacrificing the fish as in the past.

The marking of the fish is important for DNR biologists to evaluate the success of each year's stocking efforts. Beginning a minimum of a year after stocking biologist estimate how many fish in a particular area are stocked versus wild.

The DNR relies on assistance from the public to obtain any heads, known as "racks", from red drum legally taken by fishermen. The public can take the racks to specially marked freezers located near the stocked areas. Biologists use the ear bones and tissue samples from these donated fish to help assess the success of the stocking project.

"Because of the increase in the minimum size (15 - 24 inches total length) analysis of racks to determine contribution to each year class is delayed," said Jenkins. "For example analysis of the hatchery contribution to the 2002 year class was just completed recently. Stocked fish made up slightly over 6 percent of the year 2002 class in both Murrells Inlet and the May River, two of the estuaries stocked that year. This is encouraging as the fish we are stocking now are much larger and should make an even bigger contribution."

Revenues from the South Carolina Saltwater Recreational Fishing License Program support this project's goal to increase the abundance of the state's most popular saltwater game fish. "The fishermen themselves play a key role in both funding and data collection for the red drum restocking program," Jenkins said. Funds from the S. C. Sea Grant Consortium and the US Fish and Wildlife Service Sport Fish Restoration Act also support the program.