Exotic aquatic species in the Patos Lagoon estuary and adjacent areas in Southern Brazil

Abstract Exotic and invasive species are considered the second major cause of biodiversity loss in the world. In addition to damage to native biodiversity, impacts caused by exotic species can affect ecosystem services and socioeconomic activities. The Patos-Mirim lagoon system (PMLS) has great ecological importance and supports important socioeconomic activities in southern Brazil. This study aimed to compile historical records of the occurrence of exotic aquatic species in PMLS and to synthesize this bioecological information, means of introduction of such species, main impact mechanisms, and undertaken management measures. The data were obtained by a bibliographical review using the official list of Invasive Exotic Species of the Rio Grande do Sul State, the National Base of Invasive Exotic Species (Hórus Institute), and scientific information. We found records of 26 exotic aquatic species in the PMLS. Actinopterygii was the most representative (11 species), followed by Hydrozoa (three), Malacostraca (two) and Bivalvia (two), and other eight classes with only one species each. In total, nine species that had been registered in the study area were ignored by the official list of exotic species for the region. The main ways of introduction were associated with socioeconomic activities, such navigation and aquaculture. The main impact mechanisms of exotic aquatic species refer to competition (85% of species) and habitat modification (46% of species). Despite the undertaken management measures, occurrence of exotic aquatic species is growing and may seriously threaten native biodiversity and its ecosystem services.