Estudo dos efeitos de diferentes estratégias de manejo para duas espécies de peixes economicamente importantes

Abstract

Most of the freshwater fisheries on the natural stocks of South America are under the effect of overfishing or near their biological limit. Among the various fish that have been suffering from the effects of selective fishing, we highlight the Pintado (Pseudoplatystoma corruscans) and the Dourado (Salminus brasiliensis). Santos, Martins e Pompeu (2012) proposed an individualbased model that takes into account the evolutionary effects of selective fishing on the exploited population. This model is an adaptation of the Penna model, based on the biology of pintado. This work had as objectives: i) based on the actual catch and fishing effort of the pintado obtained during the monitoring carried out by Okada et al. (2010), to calibrate the model proposed by Santos, Martins e Pompeu (2012) in the rivers of the reservoir of Manso-Cuiabá, MT, in the period from 2000 to 2008, so that it can be used as a model for forecasting catch for the stock of painted in that region, and from there, to study the effect of the selective fishing subject to different curves of selectivity. As the correlation between actual and simulated catch results for the pintado was 92.21%, it is possible to make catch forecasts with annual estimates of the number of fishing days for the studied region. It was also verified that the selectivity curve using the capture window (90 L 115 cm) was more sustainable for the species than the logistic (L 85 cm) in all the population and phenotypic characteristics studied, except of catch; ii) to evaluate the effect of different moratorium periods on the population and phenotypic characteristics of gilt. It was verified that the selective fishing without and with moratoria of 5, 15 and 50 years did not present significant differences for the dourado species; iii) to investigate the effect of different selectivity curves for the fishery from the bioeconomic point of view using Gordon-Schaefer’s model (GORDON, 1954). It was confirmed that for a population with no probability of mutation in the phenotype (w = 0), the best selective fishing strategy was the logistic selectivity curve (L 85 cm), and for a population with a probability of mutation in the phenotype (w = 0; 5), the best option was the fishing strategy using the catch window (90 L 115 cm) and, iv) finally, to introduce into the model proposed by Santos, Martins e Pompeu (2012) the capture proportional to the population density and to compare it with the conventional selective fishing already applied in the capture of the pintado. It was verified that fishing using the new approach, proportional to the population density, was more sustainable than the conventional selective fishing adopted by the current Brazilian legislation (L 85 cm) for all phenotypic characteristics (I m , k e L m ), an advantageous result for the species.