Macrocrustaceans distribution in Laguna Mecoacan, south Gulf of Mexico

Abstract

Dredging the inlet of Laguna Mecoacán, Tabasco, southern Gulf of Mexico in 2000, affected the distribution of aquatic fauna after modifying the volume of water, salinity gradient, and migration patterns between estuarine and marine organisms. Ten sites were bimonthly sampling during the day in February, April, June, August and October 2000. A total of 702 decapods belonging to nine families, 14 genera and 19 species were collected with an otter trawl. Dominant species in density (ind/m2) were Eurypanopeus depressus, Litopenaeus setiferus, Farfantepenaeus aztecus, F. duorarum and Clibanarius vittatus, whereas for biomass (g/m2) the penaeids, C. vittatus and the swimming crabs Callinectes rathbunae, C. similis and C. sapidus were dominant. The highest density (61%) was recorded in the rainy season, whereas the highest biomass (57%) was obtained in the dry season. The spatial variation in salinity is reflected as a gradient from the southeast to the north, defining three zones due to the marked fluctuation of the river discharge. The 81% of the species, 87% of the density, and 77% of the biomass of all decapods were collected in mesohaline and  polyhaline conditions (zones II and III), and the minimum values in oligo-mesohaline conditions (zone I). The lower number of decapod species in Laguna Mecoacán, in comparison to other coastal lagoons in the southwestern Gulf of Mexico, is related to the restricted distribution of the submerged aquatic vegetation and the prevalent oligohaline and mesohaline conditions, while habitats as seagrass and macroalgae beds, and the mussel and oyster reefs have drastically decreased, and the unvegetated muddy substrates are predominant in this lagoon.