Toxicidade aguda da amônia em Piaractus mesopotamicus

Abstract

The presence of nitrogen composts may affect the economic performance of fish farming. Currently, there is little knowledge related to how native fish species tolerate different levels of composts in aquaculture systems. Concentration of ammonia may vary considerably and become toxic. This is frequent when fish systems are handled with little attention to water parameters. The present research aimed to evaluate the tolerance of Piaractus mesopotamicus. Fish were challenged using different concentrations of ammonia. The experiment was developed in aquariums by monitoring blood parameters and water. Fish weighed 268±71g and measured 20.7±3,08 cm (standard length). After fasting, six repetitions of Piaractus mesopotâmicos were exposed to concentrations of NH4Cl (0.0 (control group), 0.1; 0.2; 0.4; 0.6 e 0.8 mg.L -1 ) in aquariums during 96 hours. Parameters of the quality of water were monitored every 24 hours. Mortality was verified at intervals no longer than twelve hours. The evaluation of blood parameters was developed only on fish that survived full-time exposure. As a result, toxicity of ammonia was observed with 1.674 mg.L -1 de N-NH3. With this dosage, mortality of fish (50% of the population) was observed after 66.75 hours of exposure. After 92.5 hours of exposure, mortality was 100%. High levels of glucose was observed with the dosage of 0.4 mg.L -1 (NH4Cl). With higher doses, no fish survived full-time exposure. This was probably due to stress. The research delivers novel data regarding the tolerance of Piaractus mesopotamicus to different concentrations of ammonia.