Linkages between salt marshes and other nekton habitats in Delaware Bay, USA

Although the importance of salt marsh habitats for fishes and crabs has been accepted for nearly a half century, the linkages between marshes and adjacent estuarine habitats have been ill-defined. In this synoptic study (n 19,000 samples, 14 species, 10 million individuals), we provide fresh insights into the patterns of fish and blue crab habitat use for the Delaware Bay and River (upstream to tidal fresh water) over 211 km of aquatic habitats. Our examination was based on 7 years (1998-2004) of sampling (with multiple gears) across 12 habitat types along the entire salinity gradient. While this study reinforces the importance of salt marsh creeks as fish and blue crab habitat, it also makes clear that there are few marsh-dependent species because almost all species simultaneously use a variety of other bay and river habitats. The pattern of use varies over seasons and with ontogeny. This facultative use of marshes, due in large part to the extensive migrations for many of the species, makes an improved focus on the linkages across this ecoscape critical to understanding the functional significance of marshes (and estuaries) to fishes and crabs and their continental shelf metapopulations.