Relação estoque-recrutamento e efeito potencial da perda de conectividade longitudinal nas áreas de desova de Brycon hilarii (Characiformes, Bryconidae) na Bacia do Alto Rio Paraguai

Abstract

The loss of longitudinal connectivity causes interruptions in the migratory routes of fish, causing damage to the reproduction of several species, inducing the fragmentation of spawning areas and considerably affecting the initial recruitment. The objective of this work is to describe the stock-recruitment relationship, identify possible spawning areas and evaluate the potential effect of river fragmentation by dams on the initial recruitment of the Brycon hilarii species in the Upper Paraguay Basin. With this in mind, our hypothesis is that the number of recruits is predicted by the size of their stock and that the reduction of potential spawning areas will cause a population reduction of B. hilarii individuals, by affecting the initial recruitment. The present study was carried out in the Upper Paraguay Basin (BAP), especially in the plateau region where hydroelectric projects in operation, under construction and those that are in different phases of studies or processes to obtain authorizations for installation are concentrated. Capture per Unit of Effort (CPUE) estimates were used as a proxy for the abundance of B. hilarii in the BAP. The results of the analysis of the relationship between CPUE and recruitment evidence the need for conservation of the areas considered as ichthyological nurseries, the sub-basins where they obtained the highest values in these analyzes were the ones that presented the greatest amount of free stretches for the species migration. Fragmented subbasins, with lesser amount of free stretches for species displacement, added little in the CPUE and stock-recruitment analyses.