Longitudinal habitat disruption in Neotropical streams: fish assemblages under the influence of culverts

Negative impacts of mining on Neotropical freshwater fishes

Abstract Mining activities have significantly affected the Neotropical freshwater ichthyofauna, the most diverse in the world. However, no study has systematized knowledge on the subject. In this review, we assembled information on the main impacts of mining of crude oil, gold, iron, copper, and bauxite on aquatic ecosystems, emphasizing Neotropical freshwater fishes. The information obtained shows that mining activities generate several different disturbances, mainly via input of crude oil, metals and other pollutants, erosion and siltation, deforestation, and road construction. Mining has resulted in direct and indirect losses of fish diversity in several Neotropical waterbodies. The negative impacts on the ichthyofauna may change the structure of communities, compromise entire food chains, and erode ecosystem services provided by freshwater fishes. Particularly noteworthy is that mining activities (legal and illegal) are widespread in the Neotropics, and often located within or near protected areas. Actions to prevent and mitigate impacts, such as inspection, monitoring, management, and restoration plans, have been cursory or absent. In addition, there is strong political pressure to expand mining; if – or when – this happens, it will increase the potential of the activity to further diminish the diversity of Neotropical freshwater fishes.

When roads cross streams: fish assemblage responses to fluvial fragmentation in lowland Amazonian streams

ABSTRACT Roads affect biodiversity by increasing mortality rates, habitat loss, and natural landscape fragmentation. Poorly installed culverts can impound streams, changing the environmental conditions, and affecting aquatic communities. We evaluated the effects of road crossings on the taxonomic composition and functional structure of fish assemblages in lowland eastern Amazonian streams, Brazil. We tested the hypothesis that the presence of road-derived impoundments affects assemblage taxonomic and functional composition and structure. Two predictions were addressed: (1) Species and functional group composition will differ in impounded reaches in relation to lotic reaches; (2) Assemblages in downstream lotic reaches will be richer in species and functional groups in relation to upstream lotic and impoundment reaches. We sampled five streams crossed by roads presenting impoundment formation, conducted by visual census (day, dusk, and night) in 200 m line transects. Assemblage composition from lentic reaches was different from lotic reaches, and Shannon diversity from downstream reaches was different from upstream and impoundment, however, beta diversity partitioning between lotic reaches showed higher nestedness contribution, reinforcing the role of impoundment in limiting fish dispersal between lotic reaches. These results suggest that impoundments impose environmental and dispersal constraints to fish, affecting their longitudinal distribution in streams fragmented by roads.

Survey of fish species from plateau streams of the Miranda River Basin in the Upper Paraguay River Region, Brazil

Abstract The objective of this study was to provide a comprehensive list of the fish fauna of headwater streams of the Miranda River in the Upper Paraguay River Basin. Our primary data set was constructed from sampling of fish using a rectangular sieve, trawl, and gill nets from 2004 to 2015. Our secondary data were derived from published reports conducted in the Miranda River Basin, in addition to taxonomic and distribution data from other studies conducted in the basin. All data were compiled, which in the end encompassed a period from 1999 to 2015. The datasets yielded a total of 143 species, 104 from the primary data (72.7%) and 39 from the secondary data (27.3%). Species were distributed among seven orders and 30 families were found in the Miranda River Basin. Characiformes and Siluriformes were the predominant orders, and the families Characidae and Loricariidae had the greatest number of species. Our results indicate a greater number of species compared to other studies of the Upper Paraguay Basin headwaters, likely due to the longer time frame covered by our primary and secondary datasets.