Diel and seasonal variation of abundance, richness and dominant species of fishes, in an estuarine soft bottom environment

Abstract

The diel and seasonal changes of a fish community in Pueblo Viejo coastal lagoon, Veracruz, Mexico, were analyzed through six two-monthly 24-h cycles. A total of 17,660 individuals corresponding to 54 species were captured using a seine beach net. The dominant species were: Anchoa mitchilli, Cathorops melanopus, Membras martinica and Bairdiella chrysoura. The most important families were: Sciaenidae, Ariidae, Engraulidae, Gerreidae and Gobiidae. Five species, Prionotus tribulus, Eucinostomus gula, Centropomus mexicanus, Cynoscion nothus and Lupinoblennius nicholsi represent new records for this ecosystem. The environmental variables did not show significant differences among hours (Ps> 0.9), whereas the number and weight of captured individuals showed a regular pattern with a maximum peak at dusk, high values during the night, eventual smaller pulses at dawn and low values during the day. The abundance was significantly greater during the night in four of the six cycles analyzed (Ps< 0.05). Species richness was always greater during the night. In contrast, the number of dominant species was regularly greater during the day. The dominant species during the night was A. mitchilli, while M. martinica and A. mitchilli predominated during the day. Total fish capture, species richness and dominant species index were not significantly correlated (Ps>0.05) with tide, salinity or temperature. Therefore the diel variation of community structure seems to be mainly influenced by the light-darkness cycle (day and night), and this can be related with feeding and predation avoidance strategies. Although monthly means of the environmental variables did not show significant correlation with the community parameters (Ps>0.2), the behavior of the fish community structure seems to be mainly determined by production processes, rainfall and salinity.