Abstract
The colonization pattern of fish assemblages in streams is often studied in the context of environmental filters. On the other hand, when fish assemblages are subjected to anthropogenic effects, variables associated with environmental quality assume more importance. Therefore, this work evaluated the richness and composition of fish from streams sampled at different urbanization levels, aiming to determine any direct effects on the structure of fish assemblages. To accomplish this, samples were collected from 2003 to 2011 at 31 sites distributed among 3 microbasins in the Rio Ivinhema Basin, Alto Rio Paraná. Based on environmental variables, physicochemical of the water and analysis of the use and occupation of the soil, the microbasins were classified into different urbanization levels (low, medium and high). A total of 4,320 individuals were sampled, out of which 57 fish species were recorded. Sampled sites with medium urbanization level presented higher richness compared to sampled sites with high urbanization level which presented lower richness. Species richness in these sites was explained mainly by water temperature and water velocity. Results confirmed that urbanization does directly affect environmental integrity, which, in turn, can lead to the homogenization of stream assemblages.
Highlights
Local communities are influenced by habitat characteristics, as well as biotic and environmental factors (Hoeinghaus et al, 2006)
The most abundant species sampled in areas with low urbanization level were Piabarchus stramineus (17.5%), followed by Serrapinnus notomelas (14.4%) and Astyanax lacustris (13.3%); at the medium level, they were Corydoras aeneus (16.9%), followed by Hypostomus ancistroides (14.9%) and Serrapinnus notomelas (14.4%), and at high level, they were Serrapinnus notomelas (45.4%), Poecilia reticulata (28.7%), and Corydoras aeneus (6.5%)
Studies reporting changes in fish communities in rivers and streams have emphasized that environmental modification, including changes occurring through the effects of urbanization, can directly influence species composition and diversity (Felipe and Súarez, 2010; Casatti et al, 2012), as well as reproductive biology (Limburg and Schmidt, 1990)
Summary
Local communities are influenced by habitat characteristics, as well as biotic and environmental factors (Hoeinghaus et al, 2006) The importance of these factors in shaping species distribution, abundance (Hoeinghaus et al, 2006) and richness (Johnson et al, 2004) often depends on the spatial scale analyzed (Jackson et al, 2001). Many stream ecosystems have experienced environmental changes caused mainly by land use, such as urban expansion (Chaudhary et al, 2018; McDonald et al, 2020) and subsequent increase in human activities in stream. Biotic and abiotic factors influence the abundance and distribution of fish in impacted streams (Paul and Meyer, 2001) owing to various environmental changes (Alexandre et al, 2010; Daga et al, 2012; Peressin and Cetra, 2014)
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