Spatial and seasonal variation in littoral fish assemblages of four estuarine lagoons on the Mexican Pacific coast

Abstract

The shallowest zones of coastal lagoons are particularly appropriate nursery habitat for many fish species by providing refuge from predators and abundant food, among other benefits. However, little is known about the characteristics of fish assemblages and their relationship with environmental factors in these areas. The main objective of this study was to investigate the abundance and composition of the fish assemblages in the shallow zones (≤1 m) of four coastal lagoons in the Central Mexican Pacific and determine the correlation of their spatial and seasonal variations with selected abiotic variables. Fish samples were taken with a beach seine in the months of May and December during two consecutive years. Simultaneously, the physical and chemical variables of the water were measured, and the particle size of the sediment and content of organic matter were determined. A total of 26016 fish belonging to 60 species were collected, but only eight species (Poeciliopsis turrubarensis, Lile stolifera, Poecilia butleri, Eucinostomus currani, Anchoa sp, Gerres simillimus, Atherinella guatemalensis and Mugil setosus) accounted for more than 80% of the specimens. Significant differences in the composition of the fish assemblages between lagoons were found. The changes were principally related to the type of communication with the ocean, second to physical and chemical variables, primarily salinity, followed by size of the sediment particles (% of mud or sand). Observed seasonal changes could have been related to environmental and biological factors (e.g. recruitment) acting synergistically. No evidence was found that the state of eutrophication of the lagoons is severe and could be affecting the composition of the fish assemblages.