Efficacy of formalin and povidone-iodine disinfection techniques on the eggs of three marine finfish species

Surface disinfection trials were performed on eggs from three marine finfish species: California yellowtail (CYT; Seriola lalandi), white seabass (WSB; Atractoscion nobilis) and California halibut (HA; Paralichthys californicus). All three species were spawned from captive populations maintained at the Hubbs-SeaWorld Research Institute (HSWRI). Five disinfection treatments were used for each species; Treatment 1 included 100 mg L-1 of formalin (F100) for 60 min (current HSWRI treatment), Treatment 2 included 1000 mg L-1 of formalin for 15 min (F1000), Treatment 3 included povidone-iodine of 50 mg L-1 for 15 min (PI50), Treatment 4 included povidone-iodine of 100 mg L-1 for 10 min (PI100) and Treatment 5 involved a control with no chemical treatment (CONT). For each treatment, the per cent egg hatching rate, per cent survival to first feeding and notochord length at the time of hatching to the nearest 0.1 mm were recorded. Bacteria were also cultured from eggs after treatment to determine the effectiveness of each treatment in reducing the bacterial counts (CFU mL-1). Treatments F100, F1000 and CONT yielded the highest hatch rates for each species (70-80%), whereas treatments PI50 and PI100 yielded the lowest hatch rates (0-2%). There were no significant differences in survival to first feeding or notochord length, which suggests that the disinfection treatments did not have a negative effect on the yolk sac larvae. The PI50 and PI100 treatments had the lowest bacterial colony counts, showing almost zero bacterial growth. The highest bacterial growth occurred in the F100, F1000 and CONT treatments. Based on the results from this study, the F100 treatment provided the best balance of disinfection and larval health for CYT, WSB and HA.