Anesthesia in pirarucu by benzocaine sprays in the gills

Abstract

Pirarucu (Arapaima gigas) is a fish that may achieve more than 2m and 100kg. Thus handling of this fish may impose risks to workers. In this way, anesthetics are imperative for safety at work, but usual anesthetics baths are not feasible for pirarucu because of the fish size and the species pulmonary respiration. Pirarucu may die drowned if submersed as the other fishes in anesthetics baths. Therefore, this work tested the possible use of benzocaine directly sprinkled in the gills of pirarucu. In the first experiment, benzocaine solutions in concentrations of 25, 50 and 75mg L-1 were tested for adult fish (55.1±7.0kg e 1.80±0.1m). In the second one, the anesthetic in concentrations of 50 and 100mg L-1 were tested for juveniles (6.0±0.6kg e 87.2±5.6cm). Benzocaine sprinkled directly in the gills of pirarucu showed to be an efficient anesthetic both for juveniles and adult fish. It was observed absence of movements during 2min, time enough for most handling procedures. No mortality occurred even one month after experiments.