Spatial and temporal structure of fish assemblages in a hyperhaline coastal system: Ria Lagartos, Mexico

The spatial and temporal fish species assemblages were analyzed throughout two annual cycles (2004-2005 and 2007-2008) in the Ria Lagartos Lagoon system, Mexico, via non-parametric multivariate analyses. We compared density and biomass of fish species among five habitat types defined by combinations of structure and environmental characteristics (hyperhaline, rocky, seagrass, channel, and marine), and three climatic seasons (dry, rainy, and northerlies). A total of 11,187 individuals distributed in 32 families and 63 species were collected. The most numerically abundant species were Floridichthys polyommus and Cyprinodon artifrons, while Sphoeroides testudineus contributed to the greatest biomass. Species composition consisted mainly of estuarine and euryhaline marine species. Spatially, a saline gradient was observed with marine conditions in the mouth, and increasing to over 100 in the inner zone of the system. Species richness, diversity and biomass declined from the mouth to the inner zone, while density showed an inverse tendency, with the highest values in the inner zone. Thus the salinity was the variable that best explained the spatial fish assemblages' structure. The ichthyofauna composition did not change over time, but the dominant species varied with the years. The abundance of juvenile specimens, suggest that the different habitats are used as feeding and breeding zones; hence it is proposed that protection strategies be pursued not only for the lagoon system but also for the northern zone of the Yucatan Peninsula.