Bonnethead Sharks, Sphyrna tiburo
Bears Bluff National Fish Hatchery (BBNFH) recently partnered with researchers from the South Carolina Department of Natural Resources (SCDNR) on a project involving wild caught, adult bonnethead sharks, Sphyrna tiburo. Because of the increasing popularity of the bonnethead fishery in South Carolina, researchers are attempting to collect age and growth data to assist with management of the species.
Sharks are captured using gill nets, tagged externally, and injected with oxytetracycline (OTC) in hopes that a mark will form on the cartilaginous tissues of the vertebrae. Sharks are held by hatchery staff in 10-foot circular tanks for 30 days because of an FDA mandated 30 day withdrawal period for OTC. While held in captivity, sharks are fed a variety of natural diets including blue crab, fish and shrimp.
Results indicate a high recapture rate in waters near the hatchery. In fact, SCDNR biologists regard these waters as some of the best habitat for bonnethead sharks in the Charleston area. Seventeen adult bonnethead sharks have been held in captivity and successfully returned to the wild. Upon release, researchers verified tag numbers, measured each shark, and briefly examined the health of each individual. Attempts will be made in following years to recapture tagged sharks from the study. Once a shark is recaptured, the OTC mark will help researchers determine an annual growth rate estimate for these unique animals.