A structured deepwater fish community in an isolated benthic feature off Southern California

Abstract

Between September and November in 1995 and 1998–2011, we conducted surveys of demersal fishes and their associated benthic habitats using direct observations from human-occupied vehicles over the Footprint, an isolated submerged ridge located seawards of the Santa Cruz Island-Anacapa Island Passage, Southern California, extending over bottom depths of about 94–500 m. The observed fish fauna, consisting of 127,351 individuals of at least 79 species, was dominated by rockfishes (genus Sebastes; 94.5% of individuals, 47% of species). The Footprint is home to a complex of benthic habitats that are occupied by a number of fish assemblages. These were defined by bottom depth, habitat type, and the environmental tolerances and preferences of each species. While the habitat-limited benthic species that occupy the shallower parts of the Footprint are isolated from the Santa Cruz Island and Anacapa Island shelves, the fishes living on the Footprint are not reproductively isolated. Rather, through a web of connections, the fishes of the Footprint are likely well integrated into the Southern California Bight. This connectivity, flowing towards and away from the Footprint, means that events hundreds or thousands of kilometers away may have profound effects on the fish assemblages on this feature. For example, economically important species were relatively uncommon, possibly the result of past overfishing locally and a lack of immigration from other regions.