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Natural Tracers as a Tool to Inform Fisheries Management


Troy Farmer, Clemson University, Forestry and Environmental Conservation Department

5 October 2018

Natural tracers such as elemental signatures in fish otoliths and stable isotopes in various fish tissues and hard parts have been increasingly used to investigate migratory patterns, serve as markers of natal origins, and determine the degree of mixing among stocks. Natal markers have served as useful tools to study fish populations in freshwater, estuarine, and marine environments. This talk will focus on the use of natal markers to study freshwater and diadromous fishes, with specific examples from studies conducted along the northern Gulf of Mexico focused on understanding the ecological implications of largemouth bass and southern flounder residency patterns across an estuarine salinity gradient. Results from these studies indicated that southern flounder display a variety of migratory patterns across estuarine salinity gradients while largemouth bass appear to be lifetime residents within specific salinity regions (i.e., tidal freshwater, oligohaline, seasonally mesohaline environments). Subsequently, this knowledge of lifetime residency patterns was used to inform our understanding of energy allocation trade-offs, growth, and contaminant bioaccumulation in dynamic estuarine environments. Examples of how this ecological knowledge has informed management decisions will also be highlighted. In closing, ongoing and potential future studies using natal tracers as tools to understand how habitat-specific residency patterns may affect growth, sex ratios, survival, and ultimately recruitment to commercial and recreational fisheries in freshwater and diadromous fishes will be discussed.