Aspectos ecológicos da ictiofauna de riachos de um sistema de veredas

Abstract

“Veredas” are water storage systems, important for the maintenance of streams in the Brazilian savanna, the Cerrado, where researches about aquatic communities are limited. This study had as main objective evaluate ecological aspects of fish community in streams from a system of “veredas” in the Environmental Protection Area of Pandeiros River (APA-Pandeiros), as well as to determine relations between the fish community and the components of the habitat. In the first article, we evaluated (i) the trophic and morphological structure of the fish assemblage, (ii) the existence of a correlation between fish morphology and the kind of exploration of food resources, and (iii) additionally, was evaluated if species with great morphological variation also presented greater variation in the diet. In this way, the ichthyofauna and the physical habitat of 25 points were sampled. In total, there were 3665 fish, belonging to 33 species. Some of them (812 individuals belonging to 29 species) were used in the analysis of diet and morphology. The results show that the ichthyofauna studied is structured in four trophic guilds (omnivorous, detritivorous, insectivorous and piscivorous). In addition, the species were clustered into three morphological patterns related to the type of feed and position in the water column. Significant relationships (R 2 =0.38, p <0.05) between diet and fish morphology were confirmed. Besides, a significant relationship (r=0.42, p <0.05) was observed between feeding variation and morphological variation between evaluated points, which could indicating that morphologically more varied species are those with greater variation in diet. It´s discussed how the environment may be influencing the trophic and morphological characteristics and it is concluded that the evaluated community showed an interesting trophic and morphological pattern influenced by environmental factors. In the second article, the main source of carbon that supports the ichthyofauna in the streams of veredas was determined, the environmental characteristics that influenced the entry of resources to the aquatic system were also defined. Based on the results of the analysis of the stomach contents, the percentage contribution of the food categories, according to their origin (allochthones, autochthonous, debris and fish), this study determinated which carbon source supports the fish community. The linear regression model based on distance (DistLM) was used to determine the variables that influenced the kind of feed. It’s concluded autochthones resources represented the main source of organic matter that sustains the fish community. Environmental variables related to the contribution of the riparian vegetation cover, flow type, shelter for fish and substrate, explained almost completely the feeding of the fish studied in the aquatic ecosystem. The characteristics of the environment could influence the predominance of autochthonous items in the diet and the importance of riparian vegetation, which indirectly support the macrobenthos. The present study contributes to the knowledge of ecological aspects of the ichthyofauna of tropical streams . Finally, we recommend actions to preserve the riparian zones of “veredas” and microhabitats of the evaluated environments to guarantee the support of resources for the aquatic environments of the studied area.