Enigmatic armoured catfishes (Siluriformes: Callichthyidae and Loricariidae) in ornamental aquaculture: A new insight into Neotropical fish diversity

Hydrological connectivity regulates the structure and function of Amazonian freshwater ecosystems and the provisioning of services that sustain local populations. This connectivity is increasingly being disrupted by the construction of dams, mining, land-cover changes, and global climate change. This review analyzes these drivers of degradation, evaluates their impacts on hydrological connectivity, and identifies policy deficiencies that hinder freshwater ecosystem protection. There are 154 large hydroelectric dams in operation today, and 21 dams under construction. The current trajectory of dam construction will leave only three free-flowing tributaries in the next few decades if all 277 planned dams are completed. Land-cover changes driven by mining, dam and road construction, agriculture and cattle ranching have already affected ~20% of the Basin and up to ~50% of riparian forests in some regions. Global climate change will likely exacerbate these impacts by creating warmer and dryer conditions, with less predictable rainfall and more extreme events (e.g., droughts and floods). The resulting hydrological alterations are rapidly degrading freshwater ecosystems, both independently and via complex feedbacks and synergistic interactions. The ecosystem impacts include biodiversity loss, warmer stream temperatures, stronger and more frequent floodplain fires, and changes to biogeochemical cycles, transport of organic and inorganic materials, and freshwater community structure and function. The impacts also include reductions in water quality, fish yields, and availability of water for navigation, power generation, and human use. This degradation of Amazonian freshwater ecosystems cannot be curbed presently because existing policies are inconsistent across the Basin, ignore cumulative effects, and overlook the hydrological connectivity of freshwater ecosystems. Maintaining the integrity of these freshwater ecosystems requires a basinwide research and policy framework to understand and manage hydrological connectivity across multiple spatial scales and jurisdictional boundaries. Show more

Worldwide biodiversity assessments have mainly focused on species richness but little is known about the diversity of species roles, i.e. functional diversity, while this is a key facet to understanding the consequences of global changes on the ecosystem services to human societies. Here, we report the world pattern of functional diversity of freshwater fish using a database encompassing morphological characteristics of more than 9,000 species. The Neotropical realm hosts more than 75% of global functional diversity while other realms each host less than 25%. This discrepancy is mediated by high functional uniqueness in some diversified Neotropical fish orders. Surprisingly, functional diversity patterns were weakly related to functional vulnerability. In the Neotropics the loss of threatened species will cause a limited loss of functional diversity (<10%) whereas in the Nearctic and Palearctic realms, decline of the functional diversity will reach 43% and 33%, respectively, conferring a high functional vulnerability to these realms. Conservation of the Neotropical fish diversity is a key target to maintain world fish functional diversity, but this should not hide the pressing need to conserve the vulnerable fish faunas of the rest of the world, in which functional diversity is to a large extent supported by threatened species. Show more