Surface Disinfection and Removal of Adhesiveness from Rainbow Smelt Eggs

The survival of rainbow smelt Osmerus mordax embryos was evaluated after treating fertilized eggs with tannic acid (150, 300, 600, or 1,200 mg/L) in suspension for 10 min to remove adhesiveness or treating them with calcium hypochlorite (25, 50, 75, or 100 mg/L), polyvinylpyrrolidone iodine (PVP-I; 25, 50, 75, or 100 mg/L), or hydrogen peroxide (H2O2; 500, 1,000, 1,500, or 2,000 mu L/L) for 15 min to achieve surface disinfection. Nonlethal concentrations of egg disinfectants were also evaluated for their germicidal effects by culturing disinfected eggs in sterile Bacto Tryptic Soy Broth. The hatching success of the eggs treated with tannic acid (at all concentrations) was not different from that of the controls. Disinfecting eggs with H2O2 (all doses) and low doses of calcium hypochlorite (25-75 mg/L) or PVP-I (25 mg/L) did not reduce embryo survival, but exposure to calcium hypochlorite and PVP-I at higher concentrations (100 mg/L and 50, 75, or 100 mg/L, respectively) was lethal. In the first disinfection trial both H2O2 and PVP-I (25 mg/L) prevented bacterial growth, but only H2O2 at 2,000 mu L/L did so in the second trial.