Biological invasions in brazilian freshwater ecosystems: present situation of alien fish species and assessment of environmental factors as invasion drivers

Abstract

Biological invasions are a global consequence of a world increasingly connected and impacted by human actions. The expansion of human activities, such as construction of dams, aquaculture, fishing and urbanization, has been transforming the structure, dynamics and functioning of freshwater environments and, consequently, favoring the establishment and invasion of alien fish species. The number of invasive alien species tends to increase indefinitely over time, which can cause numerous and severe impacts on recipient environments, such as changes in ecosystems and native species extinction. Understanding the biological and ecological aspects of introduced species, as well as identifying which habitat variables are favorable to the establishment of these species, are important steps to control future biological invasions and manage those that have already taken place. Thus, the aims of this study were: (I) to prepare an updated list of fish introduced in the main watersheds of southeastern Brazil (Upper Paraná, Paraíba do Sul, São Francisco, Jequitinhonha, Doce and Mucuri), informing their invasion status, category of environmental impact (EICAT/IUCN), pathways of introduction, origin and taxonomic attributes; and (II) to evaluate the relative importance of physical habitat variables on the presence and abundance of the invasive fish Poecilia reticulata, a species widely distributed in Brazil and in tropical and temperate regions. The results of this work indicated an increasing number of fish species introduced and established in the studied watersheds, compared to previous studies. There were detailed data on the distribution and population status of these species in Brazil, but a lack of ecological studies on the impacts of such introductions. The present study also highlighted the importance of urbanization in the establishment and invasion of P. reticulata. Urban areas were relevant pathways for the introduction of this invasive species, and the changes in the habitat caused by urbanization created distinct environmental conditions that benefit this species, as well as other opportunistic invaders. This result reinforces the importance of protecting the biotic integrity of watercourses for the management and prevention of biological invasions.