Abstract
We described the spatial distribution of fish trophic groups in the Agua Boa Stream, MS, Brazil. Specimens were caught using electrofishing in the upper, intermediate and lower stretches of the stream, between March and November 2008. We analyzed 415 stomach contents of 24 species. Detritus/sediment and aquatic invertebrates were the main exploited resources. Ordination analysis categorized the species in six trophic groups. Aquatic invertivores showed the highest richness (10 species), followed by detritivores (08 species), omnivores (03 species), terrestrial invertivores (03 species), algivores (02 species) and herbivore (01 species). Three trophic groups occurred in the upper stretch, six in the intermediate and five in the lower. Detritivores, omnivores and algivores showed the highest density, while detritivores and aquatic invertivores presented the highest biomass. Autochthonous resources were particularly important to the studied fish fauna, especially aquatic invertebrates, so, conservation actions reducing the simplification of the habitat by silting and recovering the riparian forest are essential to maintain the ichthyofauna of the Agua Boa Stream.
Highlights
Most fish assemblages in low order streams have common characteristics, such as small size, high endemism, restricted geographical distribution, no commercial value and dependence on riparian vegetation for feeding, reproduction and shelter (Casatti, Langeani, & Castro, 2001)
For streams subjected to siltation, removal of the riparian forest and consequent environmental simplification, it is expected a reduction in trophic groups diversity, which means the reduction of functional roles played by fish (Cross et al, 2013)
Considering the total resources consumed by the assemblage in each site, detritus/sediment was the dominant item in the diet of species in sites 2 (V=55.5%) and 3 (V=37.5%), while aquatic invertebrates predominated in Site 1 (V=37.7%)
Summary
Most fish assemblages in low order streams have common characteristics, such as small size, high endemism, restricted geographical distribution, no commercial value and dependence on riparian vegetation for feeding, reproduction and shelter (Casatti, Langeani, & Castro, 2001). These fish have a crucial role in the ecosystem dynamics since they act both as predators, regulating invertebrates and. Considering that survival, growth and reproduction of fish depend on the amount of energy and nutrients generated by feeding activity (Wootton, 1999), the knowledge of the food resources explored provides a means to understand fish population dynamics and the relationship with biotic and abiotic components. For streams subjected to siltation, removal of the riparian forest and consequent environmental simplification, it is expected a reduction in trophic groups diversity, which means the reduction of functional roles played by fish (Cross et al, 2013)
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