Growth of largemouth bass in a dynamic estuarine environment: an evaluation of the relative effects of salinity, diet, and temperature

Abstract

Some freshwater fishes occur regularly in estuarine areas that experience spatial and seasonal variation in marine influence. These dynamic abiotic and biotic conditions potentially influence food consumption and growth. We found that effects of an estuarine environment on the growth of largemouth bass (Micropterus salmoides) in Alabama's Mobile–Tensaw River Delta depended on body size, distance from the marine source, and amount of freshwater inflow. Incremental growth analyses demonstrated that young largemouth bass (<age-3) grew more rapidly downstream in the estuarine environment declining with distance upstream; this relationship was reversed for older fish with faster growth in fresher, upstream areas. The magnitude of freshwater inflow influenced the relationship between age-specific growth and proximity to Mobile Bay. Bioenergetics simulations suggest that interactions among size-specific metabolic cost of salinity, maximum water temperature, and spatial differences in both salinity and prey energetic content can explain these growth patterns. The cost–benefit of the estuarine environment to largemouth bass is not only dynamic seasonally, but also changes ontogenetically because of shifts in salinity tolerance and prey use.