Dinâmica populacional e avaliação dos estoques de duas espécies da família Pimelodidae Explotadas no Rio Madeira (RO e AM)

Abstract

The fishing in the basin of the upper and middle Madeira river contribute for most of the production landed in the Rondonia state. In this area, operate about 3,000 professionals fishermen, divided into 530 km in the Madeira River, in approximately 29 riverside communities and six districts. In 2009, with the implementation of the Monitoring Program of Fishing Activity of the Madeira river, there was a new step in the research of fisheries biology in this region. This monitoring is performed by the Laboratory of Ichthyology and Fishing, of the Federal University of Rondonia – UNIR, and includes the city of Guajará-Mirim, in the upper Madeira, and Humaitá, in the middle Madeira. Mathematical models have been used to support decisions for the management and fishery management. Thus, the simulation performance has been the basis for assessing the status of inventory and to identify possible management actions for fishing. This study aimed to characterize the fishery and to estimate the population parameters and state of exploitation, using Biological Reference Points (PRB), of two Pimelodidae with different life strategies: P. pirinampu, barba chata, lowland migratory species, and B. platynemum, babão, great migrator, with great importance for fishing in fisheries communities along the Madeira river. The records of landings per month from 1999 to 2009 with total and specific production were recovered in the Colônia de Pescadores Tenente Santana Z-1. We also used data collected during the Monitoring Program of Fishing Activity in the period of April 2009 to March of 2011 in 11 locations along the Madeira river. Through the records of landings allowed the analysis of total and specific production in kg; weight composition of catches; fishing effort; fishing devices used; local fishing periods and habitats; operating costs with the fishing activity in the region, as well as biometrics standard length (Ls, cm) and total weight (Wt, g). The data show that in the Year I P. pirinampu showed the highest production among the categories, with 92,964.8 kg. In the Year II, this species appeared in 3rd place in the landings with 42,947.5 kg. Adding the two years, the production was about 136 t representing 13.2%. B. platynemum showed production of 11,058.2 kg in Year I and 10,749 kg in the Year II, getting on 10th and 16th, respectively. Adding the two years, it produced over 23 t. The tarrafa was the most productive fishing device for the two species, registering 50 and 5 t for P. pirinampu and B. platynemum, respectively. The values of growth parameters and mortality rates of P. pirinampu compared PRBs demostrate that this species has experienced overfishing of growth in the Madeira basin, whereas B. platynemum is in a situation less threatening. It is suggested that a deep evaluation of the effectiveness of the transposition system of fishes built by the companies responsible for the operation of dams to ensure the survival of these populations from the Madeira River.