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Effluents from trout cultivation intensive system: characterization and impact over the receiving water body

Abstract

The impact of trout cultivation intensive systems over rivers depends on the size of the enterprise, management practices, nature and volume of consumed water, dilution capacity of the water body and on the bacteriological characteristics of the receiving water. Compared to the volume of studies that have been carried out abroad, in Brazil there are just few papers on trout cultivation in special involving the analysis of the quality of water discharged into the receiving body. The purpose of this project is to evaluate the environmental impact caused by a trout cultivation intensive system. Samples are collected inside a trout commercial enterprise established at Serra da Bocaina, city of Bananal, São Paulo State (1160m above sea level). Sampling stations will be built at the place involving supply points, effluent discharge and receiving water. The trout cultivation pool will be populated by fish at different development stages, i.e. larval, growing, feeding and ready for commercialization. Samples will be collected for three months once a week to evaluate the following variables: total nitrogen concentration, total phosphorus, nitrite, nitrate, and ammonia, total solid in suspension and organic matter. Additionally a multi-parameter sound was used for supplying information about water temperature, dissolved oxygen, turbidity, pH and electrical conductivity. The zootechnical parameters to be evaluated are: weight gain, apparent food conversion and gross food conversion of the cultivation system to measure the total ration supplied and the quantity extracted in each fish discharge. It is intended to relate production management with alterations of water quality thus permitting to conclude about the impact caused by the activity. With the purpose of subsidize this project and considering the terms of regulation CONAMA 375/2005 that includes ecotoxicology as a powerful tool to measure the water quality, it is also intended to perform ecotoxicological studies to evaluate occasional impacts caused to the aquatic environment (receiving water body) and thus provide technical support to the proposals for treatment of effluents. The ecotoxicological studies will be realized according to ABNT standard methodology applied to studies with test organisms Ceriodaphnia dubia and Pseudokirchneriella subcapitata, which makes it possible to read results of chronic and acute toxicity at the same time. The conclusions of such studies will help fish farmers to adopt techniques that permit them to practice trout cultivation in an environment sustainable way. (AU)

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