The South Carolina Department of Natural Resources, SCDNR, first started augmenting wild populations of marine gamefish, including red drum, in the early 1980’s through stock enhancement programs. The development of genetic tools , which identify hatchery fish compared to their wild cohort, has allowed SCDNR to use applied fisheries research to answer life history questions and improve stocking techniques to increase survival and contribution of hatchery fish.
The increase in tropical cyclones along the eastern seaboard over the past decade provided an opportunity to examine the effects these systems, primarily increased precipitation, have on hatchery survival and movement . Three tropical events occurred in South Carolina: Hurricane Joaquin in 2015, Hurricane Matthew in 2016, and Hurricane Florence in 2018. All three events were associated with record rainfall and river cresting in localized areas where stocking occurred. Genetically unique families of hatchery fish were released before and after each rain event . SCDNR’s inshore fisheries section collected young of the year red drum through their independent fisheries survey using trammel net and electro fishing gears. Each fish was measured, and a small fin clip was preserved for genetic analysis. Hatchery contribution was determined based on the percentage of hatchery fish compared to wild fish caught in the sample.
Results from all three years demonstrate that stocked fish made a larger contribution and had a wider distribution area when stocked after major rain events compared to fish stocked before these events. These findings suggest that major rain events during critically important times such as spawning and larval recruitment may have a negative impact on wild red drum recruitment and potentially subsequent contribution to the fishery . Increases in the frequency of tropical systems, their effects on the red drum population, and decreasing population trends in juvenile red drum abundance indices seen over the past decade in our independent fisheries surveys provide fisheries managers valuable information for potential regulatory efforts to combat population declines.