Desempenho de tilápia em sistema de bioflocos na fase de berçário: estudo de caso na Fazenda Água Boa, Trairi/Ce

Abstract

In Brazil, tilapia was introduced experimentally in the middle of the last century, and due to its enormous acceptability, its production grew with the passage of time. The state of Ceará followed the national trend, but it had a sudden drop in production due to severe problems with drought. As a result, the CE today only stores 21.4% of its water capacity and the reservoirs of Castanhão and Orós, the main reservoirs that support intensive fish farming in tanks in the state, have a stored volume of less than 10% of capacity. Given this reality, the current challenge for the improvement of intensive production systems is based on the reduction of the use of water for the renovation and maintenance of its quality. The Biofloc Technology (BFT) system meets these requirements and can be considered as one of the most suitable for the sustainable development of aquaculture. The objective of this work was to evaluate the quality of the water and the zootechnical performance of juveniles of Nile tilapia (Oreochromis niloticus), cultivated in a bioflocos system, in a commercial farm, in the municipality of Trairi / CE. Data from a crop cultivated during the period from December 6, 2018 to March 14, 2019 were used, making 95; 97; 98 and 99 days of cultivation, in nursery tanks 1; 2; 3 and 4, respectively. Among the water quality parameters analyzed, the temperature, oxygen, pH, alkalinity, ammonia and nitrate were within the recommended levels for fish production, but for nitrite the values were above the recommended level and could cause respiratory stress in the fish. The total sedimentable solids reached ideal values on the 57th day, but had continuous production of microbial aggregate, exceeding the recommended limit. Regarding the zootechnical performance, the survival rate varied between 82.54 and 90.29%; daily weight gain 151.0 and 177.0 g; the productivity between 7 and 8 kg m-3, smaller than that said to be supported for the production of tilapia in BFT. As for the feed:gain ratio was better than those reported in the literature (1.2 ± 0.1). It was concluded that the water quality was altered, aided by the action of heterotrophic bacteria in reducing ammonia to nitrite and nitrate and the performance was compatible with values described in the literature, allowing to say that BFT is a technology that can be used in commercial farms for fish farming.