Spatial patterns of density and size structure of penaeid shrimps Farfantepenaeus brasiliensis and Farfantepenaeus notialis in a hypersaline lagoon in the Yucatán Peninsula, Mexico

Spatial variation in the density and size structure of penaeid shrimps Farfantepenaeus brasiliensis (Latreille, 1817) and Farfantepenaeus notialis (pérez-Farfante, 1967) was investigated in Río Lagartos, a coastal lagoon with hypersaline conditions (mean salinity 58.1). We evaluated the influence of salinity, temperature, and recruit density on the density of shrimps. A total of 2060 shrimps belonging to three Farfantepenaeus species was collected on a monthly basis from November 1996 to April 1997. Of the 1349 identified shrimps, F. brasiliensis was the dominant species, accounting for 79.5% of the total catch followed by F. notialis (17.5%) and Farfantepenaeus duorarum Burkenroad, 1939 (3.0%). The remaining 34.5% were small unidentified shrimps classified as recruits (i.e., < 6.0 mm CL). Shrimps were collected only in hydrological zones with a mean salinity < 50 and were completely absent in the innermost zones (mean salinity > 60). We found a common pattern of density and size structure for penaeid shrimp species: decreasing densities and increasing sizes from outer (near sea inlet) to inner zones. Multiple-regression analysis indicated that salinity was the most important hydrological variable in the F. brasiliensis, F. notialis, and recruit catch models, showing a strong negative relationship with density. Recruit density also significantly influenced the density of F. brasiliensis and along with salinity explained 42% of the overall variation of this species. The preference of penaeid shrimps for zones proximal to the sea inlets has implications for management strategies designed to protect this resource during the artisanal shrimp-fishing season.