Density and depth distribution of the sympatric species <I>Squilla chydaea</I> and <I>Squilla empusa</I> (Stomatopoda: Squillidae) in the southern Gulf of Mexico

Abstract

The present study analyzed the density and depth distribution of Squilla chydaea (Manning, 1962) and Squilla empusa (Say, 1818) along the continental shelf in Campeche Sound during the rainy season months (July, August, October) of 2012 and 2013. Samples were collected during both day and night at 26 stations in 2012 and 34 stations in 2013. In total, 234 stomatopods were collected: 45% were S. chydaea and 55% were S. empusa. The mean densities of each species varied significantly by year (2012 > 2013) and sampling time (night > day). The highest mean density (4.7 ind ha–1) was observed for S. empusa during night in 2012, which was 47 times higher than the lowest density of S. chydaea, found during the day in 2013. The highest densities for S. chydaea were observed offshore of Terminos Lagoon and for S. empusa in the vicinity of Terminos Lagoon and adjacent to Grijalva-Usumacinta and San Pedro–San Pablo rivers. Results indicated that for S. chydaea, the relationship between density and water depth was quadratic in form, with the highest densities occurring between 60 and 120 m. The density of S. empusa decreased linearly with depth; the highest densities were observed at <30 m. For both S. chydaea and S. empusa, differences in depth distribution varied little between years. These results provide new information about stomatopod species in the southern Gulf of Mexico and are of potential interest for fisheries management and environmental monitoring.