Ecologia e manejo da pesca comercial do tucunaré Cichla vazzoleri no Reservatório da Usina Hidrelétrica de Balbina, Amazonas, Brasil

Abstract

Hydropower installations affect about one-third of the world's freshwater biodiversity and hundreds of millions of people who depend on associated ecosystem services, such as fishing. This scenario is particularly alarming when it comes to the Amazon because that region has one of the highest per capita fish consumptions in the world, supported by small-scale fisheries, widely spread and involving thousands of people. However, important information to guide the management of the activities in reservoirs is still incipient. In this context, this dissertation analyzed the commercial fishing of the peacock bass Cichla vazzoleri in the reservoir of the Balbina Hydropower, through the characterization and analysis of the structural and socioeconomic aspects and ecosystemic modeling of the activity. Interviews were carried out with the fishers who are residents in communities of Rumo Certo and village of Balbina. Most of the fishers were male, their level of education was low, and everyone was affiliated with some Fishers’ Association. The fishers owned small boats and fishing gears that were employed in the activity, and they financed their fisheries themselves. An income supplement was very important, because the income from fishing was low and variable, being subject to the seasonal behavior of the reservoir level and the market price established by the commercial intermediaries. Most fishers were able to define the current fishing agreement. They perceived changes in recent years, especially in relation to the increase in fish size and quantity and stated that the enforcement needed to be more intense as there were fishers who were didn’t abide by the established rules. In Rumo Certo, during the flood season, the catch was influenced by fisher’s age, gender and the motor’s horsepower, and during the dry season, the catch was influenced by fisher’s age and fishing time. In Balbina, during the flood season, the catch was influenced by other economic activities, and during the dry season, there were no significant variables. The costs, during the flood in both the locations, were influenced by all the variables except motor’s horsepower, and in the dry, were influenced by all variables. In the flood, Rumo Certo fishers would have to make two trips a week to maximize profit, and in Balbina taking more than one trip per week would possibly not be viable. In the dry, they start making profit only from the seventh and the tenth trips, Rumo Certo and Balbina, respectively. Finally, two scenarios were simulated to investigate the dynamics of the fish stock: (i) considered a reduction of stock replacement values to half the initial values, a 50% increase in fishing effort, natural mortality, fixed and variable costs, average fish prices, number of monthly trips and commercial fishing allowed all year round; (ii) analyzed the effect of prohibiting commercial fishing. Scenario I seemed to be the most economically appropriate, but it is bad from the ecological point of view because of the elimination of the fishing agreement. Scenario II had a little difference in relation to the BaU; therefore, to prohibit fishing altogether was not the best alternative. Nevertheless, it is important that the fisheries are continued to be monitored through a participatory system, both by users and by fishery resource managers. It is hoped that the results presented will stimulate the discourse and the efforts to improve management, and that can in turn help subsidize the fishers in their demands of socialenvironmental inclusion in policies that suit their interests.