Influences of environmental conditions in the fish assemblage structure of a tropical estuary

Abstract Three fish assemblages (functional groups according to estuary use) were examined, which presented different responses to environmental variations, mainly associated to the dry and rainy seasons and high and low salinities and temperatures in the Buenaventura Bay estuary, Colombia, Tropical Eastern Pacific. In total, 4674 individuals were collected, belonging to 69 species of 29 families. The most abundant species was Sphoeroides trichocephalus (35% of the total density). The assemblage of estuarine-resident fishes showed high tolerance to environmental variations since these were present all along the estuary and throughout the year. The assemblage of marine estuarine–dependent species was associated with the rainy season and low salinities and temperatures. The assemblages of marine estuarine opportunist fishes were associated with areas of higher environmental variability in both seasons, dry and rainy. Fish species belonging to the same functional group showed variations in their response to environmental changes which evidenced complex spatial and temporal dynamics. Understanding these changes is necessary to generate effective management plans based on scientific ecological knowledge, which include environmental impacts present in this estuary such as microplastics, heavy metals, and effects of dredging, and their effects on the ecosystem.