Structure of fish assemblages with the bioinvasion of Clarias gariepinus in a river in the Guapimirim Environmental Protection Area, southeastern Brazil.
Abstract The African sharptooth catfish ( Clarias gariepinus ) is the most important catfish species for aquaculture. It has great capacity to endure several stressing factors, such as adverse environmental conditions, as well as a broad feeding flexibility. Notwithstanding, the presence of this alien fish in the Guapimirim Environmental Preservation Area, in Southeast of Brazil, may generate negative impacts on the community of native fish. In 2018, during dry and rainy seasons, samples from the fish community were collected in thirty-two sites of the Guapi-Macacu River, and the abiotic variables (salinity, pH, temperature, turbidity, dissolved oxygen, and transparency) were assessed to diagnose which factors influence in the distribution of the alien fish along the river. Moreover, species within the ichthyofauna were evaluated as bioindicators to identify possible alterations in the community. Multivariate analyzes indicated that the African sharptooth catfish dominates the buffer zone of the environmental protection area, benefiting from higher levels of dissolved oxygen and temperature. However, C. gariepinus still do not dominate the most protected area of Guapimirim, where a higher percentage of native fish species dwell. The alterations in abiotic factors, related to the increase in the temperature, may significantly contribute to the domination of this invading alien fish in this protected area, being necessary the constant monitoring of some key species, as well as the population of the invading species in this environmental preservation area.