Efficacy of formalin, iodine and sodium chloride in improvement of egg hatching rate and fry survival prior to the onset of exogenous feeding in yellow perch

Abstract

Egg disinfection is considered the most important routine work in hatcheries to avoid fungal and/or bacterial infection of fish eggs. The aim of this study was to determine the effectiveness of three disinfectants: formalin, iodine and sodium chloride on the hatching success of yellow perch eggs. The disinfectants were tested in triplicate at different concentrations for 15 and 30 min bath treatments. Two experiments were conducted; formalin at five concentrations (25, 50, 100, 150 and 200 mg L−1) and 25 mg L−1 iodine were tested in the first experiment. The second experiment involved formalin at three concentrations (250, 500 and 1000 mg L−1), iodine at three concentrations (50, 100 and 250 mg L−1) and sodium chloride at three concentrations (500, 1000 and 3000 mg L−1) were used. Iodine and sodium chloride-treated eggs hatched earlier than formalin-treated eggs. The highest mean percentage of eyed stage, hatching rate and survival to first feeding fry was observed at 200 mg L−1 formalin for 30 min, 50 mg L−1 iodine for 15 min and 500 mg L−1 sodium chloride for 30 min. High concentrations of formalin (1000 mg L−1), iodine (250 mg L−1) and sodium chloride (1000 and 3000 mg L−1) showed toxicity to yellow perch eggs, resulting in low hatching rate and survival to first feeding fry. We recommended formalin at a concentration of 150–200 mg L−1 for 30 min as an effective, easily available and low-cost disinfectant for routine use to improve yellow perch hatchability.