Óleo de cravo como agente anestésico no transporte de juvenis de tilápia do Nilo "Oreochromis niloticus"

Abstract

Transport of live fish is a harmful stimulus to organisms homeostasis. This practice is traumatic for the animals, because it’s involves the capture, handling and storage and the displacement of individuals, until the release. This suggests the need for a procedure to reduce these stressors. The objective of this study was to evaluate the effect of clove oil in ionic and metabolic responses of juvenile Nile tilapia, undergoing transport simulation in plastic bags, in different densities. Two experiments were conducted: the first evaluated four concentrations of clove oil (four replicates each): 5, 10, 15 and 20 mg L-1, to examine fishes behavior during and after the transport simulation, survival and water quality. Twenty fishes were used per carry bag (50 g L-1): In the second experiment, only the best anesthetic concentration observed in the first experiment was used. Fishes were stored in plastic bags at densities of 16, 28 and 40 fish per bag, equivalent to 140, 245 and 350 g L-1, respectively. After a new transport simulation, the levels of blood glucose, lactate, chloride ions, magnesium and calcium were evaluated. In the first experiment, the two lower concentrations were ineffective to anesthetize the animals. The concentration of 20 mg L-1 attenuated the excretion of nitrogenous compounds, but resulted in a high mortality rate, while the concentration of 15 mg L-1 showed the most satisfactory results. In the second experiment, the anesthetic was not able to minimize the increasing levels of glucose, lactate, independent of the density used. About the ionic variables, the use of clove oil was able to maintain levels of Cl-and Ca +2, except for Mg +2. The use of clove oil showed little preventive effect on stress caused by transport simulation, and may even have acted as an additional stressor agent.