ABSTRACT

CONTENTS Introduction ............................................................................................................................................ 351 Methods.................................................................................................................................................. 353

Study Sites.................................................................................................................................... 353 Water Quality Monitoring ............................................................................................................ 354 Nekton Collection ........................................................................................................................ 354 Statistical Analyses....................................................................................................................... 354

Results .................................................................................................................................................... 355 Water Quality ............................................................................................................................... 355 Nekton Species Composition ....................................................................................................... 357 Linking Abiotic and Biotic Patterns ............................................................................................ 360

Discussion .............................................................................................................................................. 361 Conclusions ............................................................................................................................................ 363 Acknowledgments.................................................................................................................................. 363 References .............................................................................................................................................. 363

Estuaries, by nature, are habitats with fluctuating salinity due to changes in freshwater inflow and modification by oceanic processes. Natural patterns in the quantity and timing of freshwater inflow create a spatially and temporally heterogeneous environment. This dynamic condition supports a diverse assemblage of species and some of the most biologically productive habitats on Earth. Freshwater inflow directly and indirectly influences factors that control nekton species composition, including larval recruitment, reproduction, food availability, predation, competition, and physiological constraints related to osmoregulation and hypoxia (Gilmore et al., 1983; Stanley and Nixon, 1992; Cartaxana, 1994; Van Den Avyle and Maynard, 1994; Whitfield, 1999; Riera et al., 2000).