Oxytetracycline for chemical marking of piava juveniles Leporinus obtusidens: determining concentration and time of treatment

Abstract

The aim of this study was to define the concentrations and immersion periods for the chemical marking of piava juveniles Leporinus obtusidens using oxytetracycline (OTC). Twenty piava juveniles were used per treatment and submitted to six concentrations of OTC (50, 100, 150, 300, 500, 800 mg OTC L^-1) and three immersion periods (6, 12, 24 h) and one treatment as control. Scales of three fishes per treatment were evaluated under a confocal microscope with UV light. The mean values of temperature, pH and dissolved oxygen were kept at 27.4°C, 7.2, and 7.4 mg L^-1, respectively. No mortality was observed in the treatments. The presence of a chemical mark was only observed in the treatment 100 mg L^-1 24 h^-1, however it was of low intensity and discontinuous. Treatments with immersion periods of 12 and 24 h produced visible marks in 300 mg L^-1, and clear bright and continuous marks in 500 mg L^-1. Treatments of 800 mg L^-1, for all immersion periods, produced clear bright and continuous marks.