Seasonal pattern of the fish assemblage of El Conchalito mangrove swamp, La Paz Bay, Baja California Sur, Mexico

Abstract

The seasonal changes in fish assemblage structure and the importance of El Conchalito mangrove swamp was assessed from October 1996 to August 1997. A modified stationary flume net was deployed at the swamp channel just before high tide and operated continuosly until the neap tide during the full moon. A total of 35,138 fish specimens were caught, belonging to 34 species included in 26 genera and 16 families. The fish assemblage changed with seasons, the fish assemblage had the highest species richness (21) and highest relative dominance index (0.77) in summer, but the highest Shannon diversity (2.7 bits/ind.) and Pielou evenness (0.73) in winter. Fish assemblages of summer and autumn had the highest similarity (68%), which reflects environmental changes that drives a sequential pattern in community structure between summer-autumn and autumn-winter clusters. Dominant species also showed a seasonal alternation between Eucinostomus currani (autumn), Albula nemoptera (winter) and Anchoa ischana (spring and summer) by numbers, whereas Diapterus peruvianus (autumn), Mugil curema (winter), Sphoeroides annulatus (spring) and A. ischana (summer) were the dominant species by biomass. The structural analysis of the fish community revealed four dominant species, seven common species and 23 rare species. The importance of the mangrove area of El Conchalito estuary is demonstrated based on the diversity of marine fishes that use this ecosystem as primary habitat for nursery, foraging and recruitment areas, and by its low disturbed conditions.