Occurrence of a continental slope decapod crustacean community along the edge of the minimum oxygen zone in the south eastern Gulf of California, Mexico

Decapod crustaceans living in deep-water in the south eastern Gulf of California were collected during two research cruises in August 1991 and 2000. Benthic sledges were operated in the depth range of 550 to 2250 m. Vertical distribution of dissolved oxygen was obtained at selected stations and epibenthic oxygen content was measured at almost all sampling stations. A total of 31 species was collected, 21 strictly benthic and eight strictly pelagic. They belong to the Penaeoidea (five species), the Caridea (13 species), the Anomura (seven species), the Astacidea (one species), the Thalassinoidea (two species), the Eryonoidea (two species) and the Brachyura (one species). The oxygen minimum zone at bottom level represents a dispersal barrier for continental shelf species, including species known to have a wide bathymetric distribution. The deep-water decapod crustacean fauna (i.e., below 550 m) living along the offshore edge of this oxygen minimum zone is dominated by species of Munidopsis. The number of benthic species collected at the stations varied considerably, from zero to 15. The highest numbers of species were caught in the depth range of 1188-1245, where hypoxic (0.6-0.76 ml O2/l) conditions prevailed. Stations with higher oxygen content had fewer benthic species. Factors other than oxygen content, affect the occurrence of species in the area.