Spatial distribution patterns of fish assemblages in Neotropical reservoirs.

Abstract

Given the great diversity of Neotropical fish species, as well as the importance of such organisms as a link within aquatic food chains, it is essential to assess different processes that drive the spatial organization of their communities. It is known that the structure of fish assemblages varies markedly in relation to space, depending on abiotic factors, biotic interactions, and dispersion processes. However, these determining factors in the structuring of fish communities vary indiscriminately in dammed aquatic bodies. The course of large rivers has been altered due to the construction of reservoirs and the number of projects under construction or inventoried has been increasing significantly in recent decades. Therefore, evaluating how the spatial organization of fish assemblages occurs in environments (i.e., dammed), as well as unraveling the predictors associated with this organization is of extremely important for conservation purposes and the implementation of management measures. To investigate such aspects in dammed environments, in the first study three cascades of reservoirs belonging to different hydrographic basins were studied, in which the effects of these reservoirs arranged in series on the patterns of diversity, distribution and richness of the assemblages were evaluated. In the second study, 29 reservoirs located in the state of Paraná were evaluated in order to identify relationships between the organization of fish trophic guilds and environmental, spatial and morphological predictors. The results found suggest that, in most of the studied environments, the environmental changes caused by the construction of dams, as well as their morphological characteristics and modes of operation have negative effects on the diversity, distribution and abundance of fish species and exert an influence on the different fish trophic guilds.