Caracterização temporal das variáveis físico-químicas do Açude Boqueirão do Cais (Cuité – PB), no cultivo de tilápia em tanques-rede.

Abstract

The cultivation of tilapia in tanks with netting has shown a large increase in the last years. This activity, at the same time that depends on water for his accomplishment and development, can compromises the quality, determined by physical, chemical and biological parameters. The physical and chemical variable of the water can be changed by many factors, including the seasonality. The actual work had as aim analyzes the physical and chemical parameters of water in the cultivation of tilapia in tanks with netting. The study was performed in the weir of Boqueirão do Cais in Cuité-PB and was divided in rainy (February to July/2011) and dry seasons (August/2011 to January/2012). The samples were collected in the environment of cultivation, in the tanks’ lines through one bottle of 300ml and were taken to the Support Unity of the project in that weir. To perform the analysis of ammonia, the pH and the alkalinity were used the Alfakit’s reagent kit. The admeasurement of transparency, temperature and oxygen dissolved were performed in situ through Secchi’s disc and an oximeter, respectively. The results demonstrated that the rainfall indexes were compatible with the standard established to the region. With the exception of the Oxygen dissolved that presented a higher average in the rainy season (7.6 mg/L ± 0.5) and lesser in the dry season (5.6 mg/L ± 1.5), did not happen significant variation of the seasonality about the other parameters. The average temperature was 25,6 ºC ± 1,3, to rainy season, and 24,5 ºC ± 1,4, to dry season; the transparency presented an average of 39 cm ± 1.8, to rainy season, and 38.8 ºC ± 1.1, to dry season; the average values of ammonia were 0.49 mg/L ± 0.5, to rainy season and 0.28 ± 0.1 to dry season; the total alkalinity was 178.4 mg/L ± 6.4, to rainy season, and 178.1 ± 4.3, to dry season and the pH maintained constant in 7,5. Therefore, all the variables were, during the studied period, according to the established by the resolution of CONAMA 357/05 and as descript in the literature specialized.