Freshwater residence and habitat requirements of southern flounder determined by otolith microchemistry

2010-2013 - $122,388

Benjamin Walther
Department of Marine Science
The University of Texas at Austin Marine Science Institute

Abstract

Southern flounder (Paralichthys lethostigma) is a broadly distributed and economically valuable species in the Gulf of Mexico, and the most sought-after flatfish on the Texas coast. Population sizes in Texas have declined dramatically over the past two decades, and the long-term sustainability of this fishery is at risk. A key uncertainty is the degree to which juvenile southern flounder require low salinity habitats for successful recruitment. The proposed work will directly assess freshwater residency patterns during juvenile life history stages using stable isotope (87Sr/86Sr) and trace element (Sr:Ca, Ba:Ca) ratios in ear bones, or otoliths, of southern flounder from coastal habitats in central Texas. Otolith chemical markers will also be compared to analyses of water samples from several freshwater sources in the region to determine residency patterns in specific tributaries. Residency patterns will then be compared to gauged stream flows to explore relationships between habitat use and outflow rates. This work will inform management strategies that require a comprehensive understanding of habitat requirements during critical juvenile life history stages and the impact of freshwater habitat and flow regimes on population dynamics of an important fishery species.