Abstract
Central Pacific FADs aggregate both yellowfin and skipjack tuna. Standing crops of these fish may, at times, exceed several hundred metric tons around an aggregation device. At these high biomass levels, tuna may remain in the vicinity of a FAD for up to several weeks. Small FAD-associated yellowfin show a significant dietary change relative to non-FAD associated yellowfin. Eighty-four percent of the yellowfin in the FAD fish community feed almost exclusively (92% by volume) on deep dwelling oplophorid shrimps. None of the other fish species in the FAD community take advantage of this resource. Only 4 percent of the non-FAD yellowfin were found to have fed on oplophorid shrimps during the 3 year study period. The diet of these latter fish is comprised of the usual array of epipelagic organisms. There is presently no evidence to suggest that oplophorid shrimps aggregate about FADs. However, the dietary shift and utilization of deep water shrimp resources does occur and may be causal to the maintenance of the high standing crop of yellowfin in the FAD fish community. These data suggest that FADs may, for some species such as yellowfin tuna, be more than just passive attractors. These floating objects may contribute to the enhancement process by causing resident fishes to change their feeding habits to take advantage of otherwise untapped resources.