Spatial structure and bathymetric patterns of penaeoid shrimps in the southwestern Gulf of Mexico

Quantitative surveys of penaeoid shrimps (Farfantepenaeus duorarum, F. aztecus, Litopenaeus setiferus, Xiphopenaeus kroyeri, Sicyonia brevirostris and Trachypenaeus similis) were conducted in Campeche Sound, southwestern Gulf of Mexico, in October and November 2002. A total of 20 stations were located along a bathymetric gradient ranging from 8 to 50 m. Spatial patterns in density and individual size were evaluated by geostatistics and linear/nonlinear models, respectively. Variographic analysis revealed that the isotropic spherical model successfully explained the spatial population structure of F. duorarum, F. aztecus, L. setiferus and X. kroyeri. Density maps obtained by punctual kriging clearly showed a species-specific spatial segregation in high-density patches, with a differential bathymetric distribution for these four species. Spatial structure was not evident for both S. brevirostris and T. similis. Clear bathymetric patterns in individual size were observed, increasing linearly (F. duorarum, F. aztecus and L. setiferus) and asymptotically (T. similis) with depth. These patterns are in agreement with the life cycle characteristics of these species. Geostatistical methods were useful to display the spatial structure of penaeoid shrimps, both for target and incidental species.