Trophic Subsidies at the Charleston Bump: Food Web Structure of Reef Fishes on the Continental Slope of the Southeastern United States
Douglas C. Weaver and George R. Sedberry
Abstract .— Trophic relationships of dominant fishes associated with hard-bottom features of the upper continental slope of the southeastern United States are linked to pelagic prey occurring throughout the water column. Deflection of the Gulf Stream by the Charleston Bump is often associated with upwelling and increased water column productivity in this region of the southeastern Atlantic coast of the United States, leading to increased food availability along the shelf/slope margin. Planktivorous reef fishes take advantage of Zooplankton that is swept onto the outer shelf and upper slope, and are abundant in upper slope rocky habitats of the Charleston Lumps (~ 200 m depth). While upper slope reefs are numerically dominated by yellowfin bass Anthias nicholsi, a demersal planktivore, large predators of the upper slope, including snowy grouper Epinephelus niveatus and blueline tilefish Caulolatilus microps, primarily feed on benthic invertebrates. Blake Plateau reefs in the vicinity of the Charleston Bump (400-600 m depth) are dominated by vertically migrating predators such as alfonsinos Beryx spp., mesopelagic fishes and squids, and the large demersal wreckfish Polyprion americanus. Stomach contents of wreckfish reveal that vertically migrating organisms support dense aggregations of this large predator in areas of elevated topography at depths that are usually food poor.