Water quality assessment in the Chato river based on the ictiofauna as a central element of the biotic integrity index. San Juan River, Chocó, Colombia

Abstract

The notable intervention and pressure on different streams of the San Juan River makes necessary the generation of basic information for the biomonitoring of its hydrobiological resources and of course the quality of the water. In this sense, this research aimed to evaluate the water quality of the Chato River using the fish fauna as a central element of the biotic integrity index (BII), in the San Juan region. Fish samplings were carried out in three stations (Campo Alegre, Manungará, and Tadó), using a trawl, cast net, and hooks of different sizes. The application of the BII consisted of three main parameters that generally group twelve measures. The first refers to the composition and richness of species, the second to the trophic functions, and the third to the abundance and condition, the sum of the attributes is the total value of the BII, with which a system of very good condition or, on the contrary, a totally polluted environment. 788 individuals were registered, grouped in five orders, 13 families, 24 genera, and 28 species. The evaluation of the model showed Manungará as the station with the best condition with the highest evaluation category (46), indicating that it presents important elements for the establishment of aquatic life. The Tadó station presented worrying data with a value of 30, indicating poor waters for the maintenance of aquatic diversity. The results obtained clearly show the existence of changes in water quality throughout the entire water source, going from good in the Manungará station, to medium in Campo Alegre and poor in Tadó. Situation that reflects the sensitivity of the index to respond to small changes in water quality, caused by anthropogenic activities.