A survey of the deep sea bottom fishes of the Gulf of Mexico below 350 meters

Abstract

Deep sea bottom fishes obtained through dredging in the Gulf of Mexico by the Texas A&M research vessel R/V ALAMINOS are reported on. No correlation between species distribution and sediment type, within the soft bottom category, is demonstrated. The number of fishes captured, per 1000 meters of bottom traversed, decreases with increasing depth. Diversity, in terms of number of species, is greatest between 350 and 1000 meters. Fishes caught above 1000 meters are one and a half to two times larger than fishes caught below that depth. Polychaetes and crustaceans appear to be preferred as food. Three modes of feeding are recognized: (1) predation upon small, truly benthonic organisms, accompanied by ingestion of significant amounts of sediment; (2) predation upon small bentho-pelagic or planktonic organisms; and (3) active predation upon large macro-benthonic, planktonic, or nektonic animals. Lack of selectivity in feeding, within the first group at least, may account for the poor correlation between sediment type and distribution of fish species. A check list, including distributional and ecological data, of the bottom fishes of the Gulf below 350 meters is presented. Two basic elements of the ichthyofauna are recognized: (1) those species having affinities with the continental shelf fauna, and (2) those representative of the truly deep sea fauna. The first group is largely restricted to the lower continental shelf and upper continental slope, above 1000 meters. The average bathymetric range of fishes occurring below 1000 meters is about three times that of species occurring between 350 and 1000 meters. The deep sea bottom ichthyofauna of the Gulf is primarily an extension of that of the Caribbean. Sills at the entrance and exit of the Gulf are not significant barriers to dispersal of these fishes. Direction of dispersal is apparently governed by the direction of the prevailing currents.