Relação estoque-recrutamento para as piranhas Serrasalmus marginatus (Valenciennes, 1847) e S. maculatus (Kner, 1860) no rio Baía, alto rio Paraná

Abstract

The most important and, usually, the most difficult problem in fisheries sciences assessment is the relationship between stock and recruitment. The term recruitment is referred in this study as the abundance of the earliest age at which a cohort can effectively be estimated. The process of recruitment is complex, and determined by density-dependent and density-independent factors. Usually, stock-recruitment is the empirical relationship between reproductive stock and the number of recruits produced. There are several suggestions to express the stock-recruitment relationship, and an example of such attempts is the models of Beverton and Holt, Ricker and Shepherd. These models were fitted by non-linear procedure to Serrasalmus marginatus and S. maculatus populations from the Baía River. The aim of the study was to determine the best model for stockrecruitment relationship and the main mechanism related to it for both species. Competition appeared to be the limiting factor for recruitment. Shepherd (S. marginatus) and Ricker (S. maculatus) were the models that presented the best fit.