This study evaluated the spatial and temporal limnological characteristics of an aquaculture area in the Itaipu reservoir, Brazil. During a one-year period, water quality parameters were evaluated in seven collection sites using a fish culture system as the reference point. A regression analysis was performed on water transparency versus chlorophyll a and total phosphorus versus chlorophyll a. The trophic state index (TSI) was calculated using data from water transparency, chlorophyll a, and total phosphorus. In addition, a study of the carrying capacity was conducted in situations of high and low flow and rainfall based on 725 m3 s−1 and 298 mm and 34.5 m3 s−1 and 11 mm, respectively. No difference was observed in the parameters of water quality and the TSI in relation to the collection sites; these parameters only varied significantly throughout the seasons. The regression analysis showed that increased total phosphorus in the environment leads to increase in chlorophyll a concentrations and consequently decreased water transparency. Evaluation of the carrying capacity demonstrated that under conditions of high precipitation and flow it is possible to produce 623.7 tons of fish per year, which is above the total cultivated in fish farms at the study site.

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RESUMO:O objetivo com a realização deste trabalho foi avaliar o eugenol como agente anestésico para o hibrido patinga. Foram utilizados 60 alevinos com peso médio de 1,08 ± 0,17 g e comprimento total médio de 3,53 ± 0,15 cm. Avaliaram-se seis concentrações diferentes de eugenol (10, 20, 30, 40, 50, 60 mg L -1 ). Os peixes foram expostos individualmente ao anestésico para avaliação da indução anestésica, após o procedimento de anestesia, os peixes foram transferidos para aquários com água livre de anestésico, para observação do tempo de recuperação. Posteriormente, os peixes de cada tratamento foram colocados em aquários com capacidade de 30 litros para o monitoramento da mortalidade, durante 72 horas. Observou-se diferença significativa (P<0,05) para os tempos de indução e recuperação anestésica para as diferentes concentrações de eugenol. Observou-se mortalidade de animais em concentrações acima de 40 mg L -1 de eugenol. Conclui-se que a melhor concentração eugenol para a anestesia de patinga é de 20 mg L -1 , pois apresentou eficiência na indução e recuperação de anestesia, sem causar mortalidade.Termos para indexação: Anestesia, híbrido, nativos, aquicultura. ABSTRACT:The aim of this work was to evaluate eugenol as an anesthetic agent for hybrid patinga. Were used 60 fingerlings with an average weight of 1.08 ± 0.17 g and total length of 3.53 ± 0.15 cm. They were evaluated six different concentrations of eugenol (10, 20, 30, 40, 50, 60 mg L -1 ). The fish were individually exposed to anesthetic to evaluate the anesthetic induction, after the anesthesia procedure, the fish were transferred to aquaria with anesthetic free water, for observation of recovery time. Thereafter, the fish in each treatment were placed in tanks with 30 liters for monitoring the mortality during 72 hours. There was a significant difference (P <0.05) for the induction times and recovery room for different concentrations of eugenol. Mortality was observed in animals above 40 mg L -1 eugenol concentrations. It is concluded that the best concentration for the eugenol anesthesia patinga is 20 mg L -1 showed efficacy for the induction and recovery of anesthesia, without causing mortality.