Estrutura das comunidades de peixes do trecho baixo do rio Dourados-MS, Bacia do Alto Rio Paraná, Brasil

Abstract

Life forms are not equally distributed in ecosystems. Considering fish, it is common for species to occupy few or just one habitat in a body of water, and there is a correlation between environmental complexity and diversity. Furthermore, seasonality can also modify how communities are distributed. Research on the structure of fish communities in rivers is essential to understand the conditions that influence them and to stablish efficient conservation strategies. There is much concern about the preservation of the biodiversity of the Upper Paraná River basin in Brazil, given that a large part of its landscape is modified, and comprehending ecological patterns associated to the ichthyofauna is still a challenge. The Ivinhema River basin, a right-bank tributary of the Paraná River, contains little influence from hydroelectric dams and is connected to the Upper Paraná River floodplain, an area of great importance for ecological processes in the basin. The fish fauna of one of its main tributaries, the Dourados River, has practically never been documented. Additionally, its fishing resources are of extreme economic relevance regionally. Therefore, we aim to evaluate the spatiotemporal distribution of fish communities in the lower stretch of the Dourados River and characterize their structure, taking the hypothesis that mesohabitat type and hydrological cycle period would influence the ichthyofauna structure. Sampling took place during the dry and wet periods of 2024 in two collection spots of the Dourados River, Mato Grosso do Sul state, which contains four mesohabitat types previously characterized: margins and macrophyte banks, backwaters, rapids and river bottom. To sample the fish fauna, standardized collection methods suitable for each mesohabitat were used. Fish were identified by taxonomic keys, species descriptions and help from experts. Principal Component Analysis and analysis based on Generalized Linear Models were performed to determine the influence of mesohabitats and periods on the community structure. Ecological indexes were calculated to compare mesohabitats and periods. Data of the species were compiled from literature. A total of 78 fish species were surveyed in the lower stretch of the Dourados River. Of these, three are endangered, two have yet to be described, 13 are long-distance migrators, 22 are economically important and 25 are considered non-native. Total abundance was of 1,886 individuals, and the most abundant species was the characid Aphyocharax dentatus, with 375 individuals. GLM analysis showed that the dry period influenced a higher abundance of the ichthyofauna, but not its composition. The wet period showed higher richness and diversity. The margins and macrophyte banks mesohabitat influenced the abundance of ichthyofauna, and presented higher richness and diversity than the others. The composition of the ichthyofauna was significantly different in each mesohabitat. The data shows that the Dourados River is home to a diverse ichthyofauna which are strictly associated with its different environments and season dynamics. Therefore, we recommend the conservation of Dourados River’s fish fauna and aquatic ecosystem by carrying out new research and maintaining its water course without the influence of large dams.