Combining Natural and Artificial Tags to Track Southern Flounder Movement in Estuaries

Southern flounder (Paralichthys lethostigma) are estuarine-dependent flatfish that support economically important commercial and recreational fisheries in Texas; however, spawning stock biomass has decreased by over 70% since the 1980s despite increasingly stringent regulatory measures.

Effective management strategies for southern flounder require the identification and conservation of critical habitats which support the fishery and should account for potential adaptive differences in habitat use and migration strategies among local populations. This is particularly true along the Texas coast, where this temperate species is located at the southern edge of its distribution and is most susceptible to changes in temperature and freshwater inflow that vary along a latitudinal gradient.

Further evidence suggests that freshwater inflow may be critical to defining nursery habitat for southern flounder in Texas estuaries. Southern flounder are also highly mobile, utilizing both the estuarine and marine environments over various timescales; however, the timing of migration and survivorship from central-southern Texas estuaries is currently unknown.

Assessing the degree of estuarine dependence and survival will determine the necessary scale for spatially explicit management regulations to facilitate fishery production throughout the geographic range of this species, especially if exposed to disproportionate levels of fishing pressure. Therefore, this project aims to provide new insights into the estuarine residency, migration, and survival of southern flounder for a more robust evaluation of current management measures aimed at rebuilding this economically important living marine resource. Specifically, the objectives are to

1. Examine the timing of southern flounder spawning migrations as a function of environmental conditions;
2. Estimate survival and fishing mortality; and
3. Assess the frequency and duration of lifetime oligohaline habitat use.