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2016-2018 Research Projects: Sustainable Fisheries and Aquaculture

Project: Determining optimal combinations of stock enhancement and harvest reduction for population restoration of inshore cobia

Principal Investigator

Tanya Darden, Ph.D.; S.C. Department of Natural Resources, Marine Resources Research Institute

Project Number

R/CF-21

Research Description

Cobia is the target of a well-developed recreational fishery in South Carolina. In S.C. waters, the population of cobia has a genetically distinct inshore spawning aggregation of fish, separate from offshore populations. Recent estimates of inshore abundance are indicative of a declining population. Concerns over the status of the inshore cobia population in S.C. have been raised by stakeholders, including state resource managers, recreational fishermen, and charter boat captains, and conservation actions including conservation action may become necessary. Guidance is needed on appropriate restoration strategies of stock enhancement and harvest reductions to facilitate recovery of the inshore cobia population.

This project will result in the development of a detailed model of cobia population demography and genetics, providing a simulation model for use during future restoration activities. The model will have implications for fisheries management and stock enhancement and will be developed to incorporate variation in reproductive success, variability in annual recruitment, and a background of population decline. Model parameters will be validated through comparisons of simulated and empirical genetic data. The model will be used to forecast outcomes of restoration strategies combining different levels of stock enhancement and harvest reduction in terms of population abundance and genetic diversity. Most importantly, the research will provide transparent and defensible management recommendations for the successful restoration of this important natural resource.

Contact for Questions

Tanya Darden (DardenT@dnr.sc.gov)

Project: Genetic diversity in overfished and recovered black sea bass

Principal Investigator

Tanya Darden, Ph.D.; S.C. Department of Natural Resources, Marine Resources Research Institute

Project Number

R/CF-22

Research Description

The exploitation of reef fishes, such as black sea bass off the southeastern U.S., has increased dramatically since the 1970s leading to concerns over population size. The primary method of determining reef fish population status is through stock assessments, which mathematically model temporal changes of fishing mortality, fish abundance, and spawning stock biomass. A complementary method of tracking stock status is the evaluation of a population’s genetic diversity. Studies indicate that reductions in population size of fish species diminish genetic diversity, impacting a stock’s long-term sustainability and ability to recover from overfishing. By tracking temporal changes in effective population sizes and other measures of genetic diversity, it is possible to generate population data that can independently corroborate trends seen in a traditional stock assessment. Black sea bass are an excellent opportunity to explore patterns of genetic changes associated in overfished populations because information is available on their genetic structure and life history patterns along the U.S. East Coast.

This study will exam the genetic diversity of black sea bass stocks before, during, and after periods of overexploitation to further understanding of the effects of fishing on the health and recovery of these stocks and also their ability to adapt to environmental change. Researchers will quantify genetic diversity parameters in historic and contemporary populations of black sea bass using DNA samples from the S.C. Department of Natural Resources’ collection of fish otolith bones to determine changes over time. Additionally, researchers will test if temporal patterns of genetic diversity are related to changes in population abundance. The resulting project data will provide an additional indicator of the status of these species in terms of quantitative patterns of genetic diversity relative to more traditional stock assessments.

Contact for Questions

Tanya Darden (DardenT@dnr.sc.gov)