Distribution and abundance of Nematocarcinus spp. (Crustacea: Decapoda: Caridea: Nematocarcinidae) off western Mexico, eastern Pacific

Abstract Distribution and abundance of the deep-water shrimps Nematocarcinus occurring off western Mexico were analysed. One or two species were captured in 33% of the samples obtained between 122 and 2340 m depth. The first species, Nematocarcinus faxoni , was by far the most common (present in all samples containing Nematocarcinus ) and the most abundant (1972 organisms). It was distributed in the central and southern Gulf of California, off the west coast of the Baja California Peninsula, and along SW Mexico to the south (17o10’15”N). For N. faxoni , densities of up to 1187 org/ha were found. The highest densities for this species occurred between 901 and 1100 m, although it was more frequently found between 1301 and 1500 m but with lower densities. The second species, N. agassizii , was less frequent (10% of captures) and less abundant (192 organisms in total). It also presented a more restricted distribution off western Mexico, and it was found only off the west coast of the Baja California Peninsula. In N. agassizii , the highest density was 246 org/ha. Both species live below the Oxygen Minimum Zone that characterizes the Mexican Pacific offshore waters. Nematocarcinus faxoni occurs in water with 0.11 to 1.60 ml O 2 /l, but it was not collected in localities where bottom oxygen concentrations were higher (up to 2.45 ml O 2 /l); N. agassizii was found in 0.11 to 0.76 ml O 2 /l. The two species co-occurred in only 5 of the stations where the genus was found. Present contribution provides a first estimation for the density and biomass of two partly sympatric species of Nematocarcinus in the eastern Pacific, thus contributing to the evaluation of a regional potential fishery resource.