The Caridean Shrimp (Decapoda: Natantia) Assemblage in the Mesopelagic Zone of the Eastern Gulf of Mexico

Twenty two species of caridean shrimps were caught (338 midwater trawls) in the upper 1,000 m of the eastern Gulf of Mexico at 27°N 86°W. The assemblage has close affinities to that of the North Atlantic and is similar to caridean faunas world wide at tropical-subtropical latitudes. Systellaspis debilis, Parapandalus richardi and Acanthephyra purpurea, in that order, were the most abundant species and comprised 86% of the catch. The three species are strong did vertical migrators with S. debilis and P. richardi having abundance maxima in the epipelagic zone at night and the A. purpurea maximum occurring deeper at 300 to 400 m. An ontogenetic pattern with respect to depth occurs in the former two species in that juveniles are found shallower in the water column than adults at night. Twelve of the remaining 19 species appear to be weak or non-migrators found deep in the mesopdagic zone and with distributions extending into the bathypelagic zone. Several types of reproduction are apparent. Among the assemblage are small egg (e.g., P. richardi, A. purpurea) and large egg (e.g., S. debitis and Oplophorus gracilirostris) producing species and those with seasonal (e. g., P. richardi) and aseasonal (e.g., S. debilis) breeding patterns, Females are more abundant than males in S. debilis and P. richardi, with ratios of 1.6 to 1 and 2.0 to 1, respectively. Overall caridean abundance was low, totaling 0.20 to 0.23 individuals · m^-2, values which are characteristic of an oligotrophic tropical-subtropical environment.