Abstract

Estuarine environments are critical habitats for southern flounder, Paralichthys lethostigma, serving as habitat for both early life and adult stages, with adult flounder leaving the estuary to spawn in the fall/winter. Understanding the movement of fish populations that use both estuarine and coastal ecosystems and the environmental drivers that initiate migrations is critical to the conservation and management of estuarine-dependent species. Migration patterns between estuaries and the coastal environment of southern flounder have been examined in the northern Gulf of Mexico using the estuaries of Galveston Bay and Sabine Lake, Texas. Since 2021, 120 southern flounder have been acoustically tagged in Galveston Bay and 35 southern flounder have been acoustically tagged in Sabine Lake and monitored with acoustic receivers placed near shorelines and tidal passages. Southern flounder show large-scale movements out of both estuaries from November through January peaking in December, while moving across multiple receivers in the bay and through the tidal passes. This peak in egress corresponds to periods of decreased temperatures and concomitant increases in cold fronts along the Texas coast. This increase in flounder movement also corresponds to an increase in fishing pressure, making this economically valuable species more susceptible to capture and harvest while moving offshore. Results from this study shed new light on the migratory behavior of southern flounder along the Texas coast.