Desempenho produtivo e avaliação econômica do cultivo de tambaqui (Colossoma macropomum) em tanques-rede, sob diferentes densidades de estocagem no lago Tupé

Abstract

Fisheries and aquaculture are considered by the UN as a strategic activity for sustainable food security on the planet, they are able to provide high quality protein food, create jobs, wealth and improve the quality of life of the poor. Among these activities there is the pisciculture in net cages, being defined as the activity in which the fish is grown in high densities in small spaces and with the continuous flow of water. The Amazon region favors the implementation of projects for fish culture in net cages. Despite the knowledge of stocking density and volume of the cages in the growing phase, there is little information about the density in cultivation in blackwater rivers. This study evaluated the effect of different stocking densities on growth and economic performance tambaqui "curumim" (Colossoma macropomum) in net cages. The experiment was conducted in the lake Tupé inside the Sustainable Development Reserve of Tupé (REDES-Tupé), AM, Brazil. It was used a lot of 4,200 tambaqui fingerlings with average initial length of 4.72±0.15 cm and average initial weight of 4.46±0.34 g. It was used a completely randomized design with three treatments (stocking densities 50, 70 and 90 peixes.m-3) with four replications. The volume used for calculating the density was 5m³ and the trial period was eight months. In the first month the fish were fed with commercial extruded ration containing 36% CP (Crude Protein) and in the following months with extruded ration with 28% CP. The stocking rates were compared based on biological indices of survival, average weight gain, biomass by volume and apparent feed conversion. They were subjected to statistical analysis of variance (ANOVA) and multiple comparison of means by Tukey test. The oxygen and temperature were monitored by diurnal variation. The pH, electrical conductivity and water transparency were measured monthly in the morning. There were collected water samples for later analysis of ammonia, nitrite and phosphorus in the laboratory. The economic evaluation was performed using the initial investment, production, total production cost, unit production cost, income, profit, break-even point and profitability. The results showed that the best density was 90 peixes.m-3. The physico-chemical variables were maintained within acceptable levels for fish culture in net cages. The economic results obtained revealed that the tested densities have no economic viability, but the stocking density was found to be an important factor in improving the production and economic indicators. The results show that a density above 90 peixes.m-3 promotes a better feed conversion, better yield per tank and lower production cost. The economic results, by the scale of production, with the tested densities show that the culture depends directly on the production capacity and the solidarity aid to fund the whole or part of production costs.