Broad and fine-scale threats on threatened Brazilian freshwater fish: variability across hydrographic regions and taxonomic groups

Abstract

Anthropogenic environmental changes are the main cause of species extinction during the Holocene. Species have been exposed to major source of threats, such as habitat loss and fragmentation, pollution, introduced species, and harvesting, many of which are derived from specific anthropogenic activities, such as urbanization, agriculture, and damming (i.e. fine-scale threats). However, the importance of these threats on the species conservation status in a given region depends on the type of impacts they are exposed to and the susceptibility of species to these impacts. In this study, we used a database of threatened Brazilian freshwater fish species to test whether the major source of threats and the specific anthropogenic impacts to species vary across hydrographic regions and taxonomic groups. Our results showed that habitat loss is a ubiquitous major threat jeopardizing the conservation status of the Brazilian fish species. However, different fine-scale threats mediate this process across hydrographic regions and taxonomic groups. The combination of impacts from agriculture, deforestation, and urbanization affects most of the threatened species in the basins of the Northeast, South, and Southeast, including the species of the most threatened order, the Cyprinodontiformes. Damming is the main human activity affecting threatened species of Siluriformes, Characiformes, Gymnotiformes, and Cichliformes, especially in northern basins (Amazon and Tocantins-Araguaia). Therefore, we found that specific fine-scale threats influencing threatened species vary across hydrographic regions and taxonomic groups, probably due to geographic variability in the incidence of human activities and differential niche requirements and vulnerability of species to these activities.

Dazed and confused: Behavioural constraints impose major challenges to fish passage in the neotropics

“…Damming is a major threat for many freshwater fish species in the world (Dudgeon et al, 2006) including Brazil (Santana, Carvalho & Teresa, 2021). Fish passage facilities have been proposed as one of the main conservation tools for migratory fish species (Silva et al, 2018;O'Brien et al, 2019;Xu et al, 2020), although it has been pointed out that these devices may be an ineffective or incomplete solution in many cases (Pelicice & Agostinho, 2008;Birnie-Gauvin et al, 2019).…”

Large-scale Degradation of the Tocantins-Araguaia River Basin

“…Future exploitation of these deposits is a significant threat, as shown by the recent environmental disasters in southeastern Brazil (Salvador et al 2020). Terrestrial and aquatic biodiversity has responded negatively to these impacts, as evidenced by major losses in fish diversity (e.g., Araújo et al 2013;Perônico et al 2020;Pereira et al 2021;Santana et al 2021). Fish constitute a megadiverse and endemic group in the Tocantins-Araguaia basin with over 700 species (Dagosta and de Pinna 2019).…”

“…This episode illustrates how government policies, guided by short-term economic profits, ignore scientific advice and the costs of environmental degradation. Non-native organisms are incipient in aquatic ecosystems in this basin (Doria et al 2021;Santana et al 2021), and aquaculture expansion will change this scenario, triggering species invasions into other Amazonian drainage basins. The literature on socioenvironmental impacts resulting from aquaculture is vast (Agostinho et al 2007;Diana 2009;Vitule et al 2009).…”

Improving the efficiency of adaptive management methods in multiple fishways using environmental DNA

“…Dams and weirs disrupt river continuity and impede migratory fish movement [1,2]. The risks from habitat degradation due to dams are possibly much higher than those from climate change [3][4][5][6][7][8][9][10]. The focus of conservation has gradually shifted from only fish, considered as economic resources in Europe and the United States, to overall biodiversity, which includes a variety of fish [11].…”