Fish diversity and composition from San Pedro river, Balancan, Tabasco, Mexico

In the San Pedro river sub-basin, Balancan, Tabasco, Mexico, an ichthyofauna study was carried out in two subsystems; the main stream and the floodplain during the months of March 2007 to February 2008. From a total of 1035 fish were collected, 33 species, 25 genera and 14 families were identified. The Cichlidae and Poeciliidae family were the most species; four species are introduced Pterygoplichthys pardalis, Ctenopharyngodon idella, Oreochromis niloticus, Parachromis managuensis and two new records were found: P. pardalis and Potamarius usumacintae. The most abundance species were Thorichthys affinis and T. helleri and five species were least abundant: P. usumacintae, Phallichthys fairweatheri, "Cichlasoma" Nandopsis urophthalmus, C. idella and Batrachoides goldmani. The higher values of diversity and abundance showed in sites I (H'=2.52 bits) and II (lambda=0.38 sp/ind). The higher values of evenness were in sites III (J'=0.86) and IV (J'=0.99). The abundance (N-max=353) species was showed in the site II. Significant differences (p<0.05) were found between the diversity and sites comparison. Canonical correspondence analysis showed that the temperature, dissolved oxygen and depth are the most important factors in the distribution of species. Finally, the relative abundance of species in the two seasons was representative by two families; Cichlidae T. affinis, (T. helleri and Petenia splendida) and Characidae (Astyanax aeneus).