Copepod assemblages in the Gulf of Tehuantepec, Mexico

Abstract

The Gulf of Tehuantepec, in the Mexican waters of the eastern tropical Pacific, is a very productive area with a high biological complexity, as the result of a wind-induced upwelling that occurs from November to February. The main assemblages of pelagic copepods in this region were identified and analysed in this study, during the final stage of the upwelling process. Samples were collected in oblique plankton hauls using a station grid that covered neritic and oceanic waters. Copepods were separated taking 10 mi aliquots from each sample. Data of copepod abundance were expressed as ind. m(-3) and subjected to a Factor Correspondence Analysis, in order to determine the main copepod assemblages. Results indicate the presence of two main assemblages: neritic and oceanic. The neritic assemblage is located on shelf waters. Its characteristic species are Microsetella norvergica, Macrasetella gracilis, Nannocalanus minor

Centropages vitrea. Corycaeus speciosus, and Eucalanus subcrassus. The oceanic assemblage includes Copilia vitrea, Eucalanus inermis, Scolecithricella abyssalis, Haloptilus spp., and Rhincalanus spp. The composition of those assemblages corresponds to the physiography of the area, and this strong variation gradient fi um the coast to the ocean has been commonly observed in other assemblages of planktonic organisms as well.