Diagnóstico da ictiofauna do rio Formiga – MG: subsídio para o biomonitoramento ambiental.

Abstract

Issues related to the water issue are increasingly debated in congresses, forums and global events, as the pollution of water resources has been growing at an accelerated pace, requiring methods that contribute to noticing this degradation as soon as possible. One method for this identification is biomonitoring using environmental bioindicators, that is, evaluation of the response of species, populations and communities, in time and / or space, to environmental impacts. The objective of this study was to diagnose the fish fauna of the Formiga River and to relate attributes of this community with the quality of water and habitat, thus seeking to infer about the potential bioindicator of these organisms in the basin. To achieve these objectives, four hypotheses were tested: H1) the Formiga River presents spatial variation in environmental quality upstream and downstream of the urban network; H2) the Formiga River presents temporal variation in water quality in the dry and rainy periods; H3) there are fish species in the Formiga River that are sensitive to pollution, and these bioindicators are of environmental quality; and H4) the fish assemblage of the Formiga River responds, in a measurable way, to the variation in the quality of the river water, being possible its use as an ecological indicator. Four collection expeditions (two in the rainy season and two in the dry season) of fish fauna and physical-chemical parameters of the water (electrical conductivity, dissolved oxygen, pH and temperature) were carried out over two years. The characterization of the physical environment was also carried out through the application of a protocol. Indices of diversity, integrated quality, biotic integrity were calculated in addition to the calculation of CPUE and analysis of indicator species. The Formiga River, throughout the sampled section, has water of sufficient quality for the maintenance of the aquatic ecosystem, the greatest variation was in the electrical conductivity in the area downstream of the urban grid in the dry period, affecting the structure of the community in that area. However, there was no clear temporal differentiation in the other variables. In terms of environmental quality, the sampled section presented a very distinct natural area upstream of the city and a disturbed area downstream. In this work, it was not possible to classify an indicator species of good water quality, but when analyzing the structure of the assembly, mainly in trophic terms, it was observed that in the natural area, invertivorous and insectivorous species were found, considered indicators of environmental complexity, while the high abundance of omnivores in the degraded area is an indicator of a disturbed environment.