Uso de diferentes anestésicos para manipulação biométrica e transporte de peixes de água doce

Abstract

Procedures performed in fish farms, such as biometry and transport of live fish can cause disturbances in fish homeostasis, affecting stress; as a consequence of this, depression of the immune system and even death of animals can occur. Thus, five articles were carried out. In Article 1 – different concentrations of benzocaine and menthol (0, 12.5, 25, 50, 75, 100, 125 mg L-1 for each anesthetic) were evaluated in juveniles of Aulonocara nyassae. The fish were classified as Juveniles I (0.74 ± 0.31 g) and Juveniles II (3.80 ± 0.92 g) for the benzocaine test. For the menthol experiment, Juveniles I (1.01 ± 0.39 g) and Juveniles II (3.73 ± 0.78 g) were used. Independent tests were performed for each anesthetic and fish size class in a completely randomized design (DIC). Induction and recovery times from anesthesia and ventilatory frequency (VF) of the animals were measured. Concentrations between 75 and 125 mg L-1 of benzocaine for Juveniles I and 50 to 125 mg L-1 for Juveniles II are ideal. For menthol, concentrations between 50 and 125 mg L-1 can be used for both classes of A. nyassae. Therefore, in Article 2 different concentrations of eugenol and menthol (0, 25, 50, 75, 100 and 125 mg L-1) were evaluated in two sizes of juveniles of Piaractus brachypomus. For the eugenol test, Juveniles I (0.87 ± 0.20 g) and Juveniles II (17.14 ± 3.27 g) were used. For the menthol assay, Juveniles I (0.83 ± 0.21 g) and Juveniles II (16.83 ± 2.78 g) were used. Independent tests were performed for each fish size class and anesthetic in DIC. Eugenol concentrations between 50 and 100 mg L-1 were able to induce anesthesia for both juvenile size classes of P. brachypomus, while menthol was able to induce anesthesia at concentrations between 25 and 100 mg L-1 for Juveniles I and between 50 and 125 mg L-1 for Juveniles II. The use of 50 mg L-1 of eugenol was able to reduce the ventilatory rate (VF) during recovery and prevented an increase in plasma glucose, having little influence on hematological and biochemical parameters after biometry. The use of 50 mg L-1 of menthol also reduced VF during recovery and did not cause changes in blood parameters that were harmful to fish physiology. In Article 3, the physical and chemical properties of zein nanoparticles containing eugenol (NPZMA) in the anesthesia process of Oreochromis niloticus and their effects on blood gas analysis and their stability in water were investigated. Four independent tests were performed in DIC. The new method of eugenol application through mucoadhesive zein nanoparticles (NPZMA) demonstrated positive charges and easy adhesion to fish mucus. The method led to fluctuations in water quality during the observation period (1 h), although it remained within the ideal range for O. niloticus cultivation. Experiment 3 revealed similar induction times for eugenol-80 mg L-1, NPZMA-80 mg L-1 and NPZMA-40 mg L-1. Recovery time was shorter for NPZMA-20 mg L-1 and longer for NPZMA-80 mg L-1. Experiment 4 demonstrated that the concentrations tested have no effect on blood gas variables. Already, in Article 4 different concentrations of essential oil of Ocimum gratissimum L. (EOOG) were evaluated for anesthesia and their use in the transport water of juveniles of O. niloticus and their effect on VF, hematology and blood biochemistry and oxidative stress. Three independent experiments were carried out in DIC. Concentrations between 90 and 150 mg L-1 of EOOG are recommended for O. niloticus with 40 g. The use of 90 mg L-1 of EOOG prevented an increase in plasma glucose soon after anesthetic induction and 1 h after recovery, but caused changes in the antioxidant defense system, increasing reactive oxygen species in hepatic and renal tissue. The use of 10 mg L-1 EOOG in transport increased glucose values and decreased hematocrit immediately after transport. The transport of O. niloticus with an average weight of 12 g for 4.5 h can be carried out with a concentration of 5 mg L-1 of EOOG. In Article 5, different anesthetic and sedative concentrations of the essential oil of Hesperozygis ringens (EOHR) were investigated for juveniles of Colossoma macropomum. Four independent trials were carried out in DIC. Concentrations between 150 and 450 µL L-1 EOHR are recommended for anesthesia of C. macropomum with an average weight of 3 g. Concentrations of 15 and 30 µL L-1 of EOHR were able to reduce the levels of unionized ammonia during the transport of C. macropomum with 2 g; however, its use in plastic bags for long periods (24 h) should be avoided, as it reduces dissolved oxygen levels. These results are promising for the fish farming industrial chain; however, studies of anesthesia for fish that investigate the morphology and histology of tissues, in addition to the zootechnical performance of the animals, are necessary.