Largemouth Bass in Coastal Estuaries: A Comprehensive Study From the Mobile-Tensaw River Delta, Alabama

Although largemouth bass is typically thought of as a freshwater species, populations occur in estuaries throughout the US Atlantic and Gulf of Mexico coasts, often with established fisheries.  These coastal populations must deal with the physiological stresses associated with salinity variation, and are generally isolated from inland freshwater populations.  We quantified individual and population parameters for largemouth bass in the Mobile-Tensaw River Delta, Alabama during 2003-2008 in an effort to understand factors important to these coastal populations to facilitate their management.  Large individuals were rare and fish condition increased with increasing salinity influence.  Growth responses were more complex; faster growth was observed in the brackish, downstream areas for fish <age-2, while growth of older fish was faster in freshwater upstream sites.  Using bioenergetics modeling, we demonstrated that a complex combination of spatial variation in water temperature, prey energetic content, and metabolic cost of salinity was responsible.  Largemouth bass of all ages moved very little, even when salinity was 15 ppt in downstream areas.  These coastal largemouth bass populations face a number of conservation concerns, and their management will require different approaches compared to their inland counterparts, including different goals, expectations, and likely even requiring consideration as unique populations.