Abstract
Abstract Aim We investigated the long-term effects of a rural landscape on the structure and trophic organization of a fish assemblage. Methods We compared environmental data and data from fish assemblage structure and trophic organization sampled in a stream located in a rural area, within a time gap of 20 years. Results We observed only punctual changes in the environmental variables and fish structure, which may not be related to the rural landscape. In fish diet, insectivory remained predominant in all sample periods. However, when we analyzed the groups of hexapods consumed by the fish species, we found a substitution of Ephemeroptera and Trichoptera by Diptera over time. Conclusions Although the fish assemblage structure was not affected, the insectivore diet analysis showed that the stream stretch could be in an ongoing process of environmental quality loss, once the simplification in the macroinvertebrates assemblage structure over time is indicative of environmental degradation.
Highlights
The South American freshwater fish fauna is considered the most diverse in the world, with a high level of endemism and at least 50% of its species living in streams (Castro, 1999)
Aim: We investigated the long-term effects of a rural landscape on the structure and trophic organization of a fish assemblage
Conclusions: the fish assemblage structure was not affected, the insectivore diet analysis showed that the stream stretch could be in an ongoing process of environmental quality loss, once the simplification in the macroinvertebrates assemblage structure over time is indicative of environmental degradation
Summary
The South American freshwater fish fauna is considered the most diverse in the world, with a high level of endemism and at least 50% of its species living in streams (Castro, 1999). For the São Paulo State, the brazilian most populous, 66 fish species are under extinction threat in different levels, the vast majority of which are small, typical of headwater streams, and many are susceptible to various impacts that lead to environmental degradation, such as pollution from industrial and domestic sewage and siltation (Oyakawa & Menezes, 2011). Changes in the natural landscape caused by agriculture and livestock can harmfully affect streams, causing alterations in the physical environment, which results in habitat degradation and impacts on the fish communities, as decrease in diversity and variations in the composition (Roth et al, 1996). According to Casatti et al (2006), changes in geomorphological features and in landscape, resulting from the agriculture and livestock activities, can contribute to the decrease in the feeding resources supply, which may cause an increase of species with generalist diet
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