Water Quality in Cage System Fish Farm in Ilha Solteira Reservoir, SP

The physical and chemical water variables and the sedimentation were evaluated in a tilapia culture with 240 cages (14 and 20 m super(3)) located on 4.5 ha of water surface in the area of the Ponte Pensa river, in the aquaculture park of the Ilha Solteira reservoir. Monthly samplings were carried out from February 2008 to January 2010 in three sites: upstream (P1) in the place (P2) and downstream (P3) of the cages fish farm. The values of pH, total ammonia, nitrate, chlorophyll "a" and total dissolved solids remain within recommended by Resolution n degree 357 of the National Council of Environment to water bodies for aquaculture. The lower dissolved oxygen concentrations were observed at the site P2 in almost all months, but the values were above 4.0 mg L super(-1) and 60% saturation. The principal component analysis showed a trend of clustering of sampling units from the central area of the fish culture, because of the total dissolved solids concentration and sedimentation rate of total phosphorus, indicating that the fish culture directly influenced the increased levels of sediment. However, in general, the tilapia culture in cages caused a disturbance of low intensity in the aquatic system. The area of Ponte Pensa river proved efficient assimilation capacity of the disturbances caused by the production process, mitigating the impact of organic load from the feeding and fish metabolism.Original Abstract: Foram avaliadas as variaveis fisicas e quimicas da agua e a sedimentacao em uma tilapicultura com 240 tanques-rede (14 e 20 m super(3)), posicionados em uma area de 4,5 ha de espelho d'agua, no braco do rio Ponte Pensa, no parque aquicola do reservatorio de Ilha Solteira. Amostragens mensais foram realizadas no periodo de fevereiro de 2008 a janeiro de 2010 em tres estacoes de coleta: em local distante da instalacao dos tanques-rede (P1), na area de criacao (P2) e a jusante da piscicultura (P3). Os valores de pH, amonia total, nitrato, clorofila "a" e solidos totais dissolvidos permaneceram dentro do recomendado pela resolucao n degree 357 do Conselho Nacional do Meio Ambiente para corpos d'agua destinados a aquicultura. As menores concentracoes de oxigenio dissolvido foram observadas na estacao P2 em praticamente todos os meses, porem os valores ficaram acima dos 4,0 mg L super(-1) e 60% de saturacao. A analise de componentes principais mostrou a tendencia de agrupamento das unidades amostrais da area central da piscicultura em funcao da concentracao d