Analysis of fish communities along a rural–urban gradient in a neotropical stream (Piracicaba River Basin, São Paulo, Brazil)

Abstract

This study investigated the fish fauna of a stream in southeastern Brazil that runs through sugar cane-growing and urban areas that are subject to sewage discharge. It aimed to determine the importance of spatial and environmental factors on fish distributions and to assess the use of fish as indicators of the environmental conditions. A longitudinal pattern of chemical water quality was observed, with more disturbed conditions at the urban sites. Several opportunistic or tolerant and omnivorous species such as Astyanax altiparanae, Poecilia reticulata, and Astyanax fasciatus were numerically abundant at these urban sites, which resulted in a consistent increase in species density and biomass along the stream. Redundancy analysis extracted three axes, identifying a nutrient-productivity gradient associated with different species composition patterns, as also detected by the indicator species analysis. No species could be considered a potential indicator of the agricultural area in the dry season, whereas four different species were judged potential indicators of three urban sites. In order to explain species distribution, variation in species abundance was partitioned into spatial and environmental components. The latter was more important, explaining 25.4% of the variation. We concluded that the fish assemblage of the Guamium stream is undergoing the initial stages of disturbance, with pronounced effects at the urbanized area, but no detectable changes at the sugar cane sites. Therefore, fish assemblages might be used as ecological indicators to detect urban impacts in similar rivers. However, the potential use of fish to diagnose stressors in areas of sugar cane plantations should be complementary to more comprehensive studies aimed at understanding the influence of this crop on freshwater resources.

Diet and trophic guilds of fish assemblages in two streams with different anthropic impacts in the northwest of Paraná, Brazil

“…This demonstrates that even though there was availability of existing vegetation in the Morangueiro stream, the fish species inhabiting this stream consumed food resources that were more abundant in the ecosystem, such as detritus and immature Diptera. In the literature, species of Astyanax are considered to be omnivorous at impacted sites , ALEXANDRE et al 2010, and it is also well documented that this genus demonstrates considerable trophic opportunism (CASSEMIRO et al 2002, ABELHA et al 2006, TEIXEIRA & BENNEMANN 2007. However, the difference between the streams investigated in the present study was remarkable: in Queçaba, there was a greater variety of resources, enabling increased differentiation in the diets of the species, allowing them to form terrestrial insectivorous, herbivorous and carnivorous guilds.…”

“…This was mainly caused by a decrease in the abundance of invertebrates due to the instability of urban aquatic environments (JONES & CLARK 1987). Some studies addressing urban streams have detected the presence of trophic groups such as omnivores and detritivores , ALEXANDRE et al 2010. This may be the result of a degradation of the food base, which provides opportunities for exploitation by more opportunistic and resistant species (ARAÚJO 1998, FLORES-LOPES et al 2010.…”

“…as increases in generalist species and reduced numbers of trophic guilds, can occur , ALEXANDRE et al 2010, ESTEVES & ALEXANDRE 2011.…”

Diversity and distribution of ichthyofauna in streams of the middle and lower Tibagi river basin, Paraná, Brazil

“…On the other hand, some of the species collected in this study, as Astyanax bockmanni, Isbrueckerichthys cf. calvus, Neoplecostomus yapo, and Trichomycterus davisi are associated with more pristine environments (Casatti et al 2009, Jerep et al 2006) and can be affected by changes in habitat complexity, water quality and hydromorphological aspects, influenced by common activities in the basin, such as agriculture and urbanization (Walsh et al 2005, McKinney 2006, Alexandre et al 2010. We registered 4 non-native species, collected in the Uvaranal, Mandaçaia, and Engenho de Ferro streams; streams characterized for filing a degree of environmental degradation influenced by urbanization (municipalities of Telêmaco Borba and Ibiporã, Paraná).…”

Effects of abiotic variables on the distribution of fish assemblages in streams with different anthropogenic activities in southern Brazil

“…In urban streams, changes in the landscape greatly affect species distribution (Alberti et al, 2007;Fialho et al, 2008;Maloney & Weller, 2010;Alexandre et al, 2010;Cunico et al, 2012). Urban growth through construction and deforestation has increased surface runoff due to soil sealing (Paul & Meyer, 2001).…”