Impactos da variação da vazão do submédio rio São Francisco sobre a composição e estrutura das comunidades de peixes e seus efeitos na atividade pesqueira

Abstract

Dams are responsible for causing major environmental impacts, interfering in the ecological processes of populations of several fish species. The hydrological regime imposed by these enterprises modifies biological processes, altering the composition and structure of the fish communities, preventing them from renewing their fish stocks, which consequently affects the fish catch in a given region. Thus, the present work aimed to understand the dynamics of the distribution patterns of the fish community in the São Francisco River sub-medium stretch that are under the effect of the environmental conditions imposed by the hydrological control of the Sobradinho reservoir, and how this has affected fishing by riverbank populations, verifying the influence of hydrological variables on the capture of species of commercial, ecological, and social importance. To verify the existing association between the hydrological variables (mean flow, difference in flow, minimum and maximum flows, month itself) and fishing catches, the generalized additive model was used, which consists of a technique used to evaluate the relationships between a response variable and predictor explanatory variables. Theoretical models of abundance distribution (logarithmic series and geometric series) were used to verify the distribution of the ichthyofaunal community, and diversity was evaluated using the Shannon-Wiener and Simpson indexes. To verify the difference of the icriofaunistic communities between the months and seasons, showing which species contributed to the variation of the data, the principal component analysis (PCA) was used. Through the results it is evident the effects of flow on species richness and diversity, and that floods are important factors in the recomposition of fish stocks, and that the species most affected by hydrological control are migratory species that need to explore a wide area during their life cycle. Furthermore, it was found that some hydrological variables maintain a positive association with fish catches in the São Francisco River sub-medium, showing that hydrological effects on fish abundance can lead to predictions of fishing yield. The best catches were obtained with flows between 900 and 1,600 m³/s, but these flow values could be different depending on the type of species and how their biology functions in relation to hydrological variables. Finally, studies like this one are important to understand the dynamics of the behavior of the species, and how this can influence the fishing catches, being essential to draw management and conservation plans to keep the ecosystem balanced, as well as to guide the appropriate way to build new developments that may be planned in the region.