Chemical surface disinfection of eggs of Baltic cod, Gadus morhua L.

The effect of two disinfectants on eggs and larvae of Baltic cod, Gadus morhua, was investigated. The eggs were disinfected for 10 min using various concentrations of either glutaraldehyde (100, 200, 400, 600 and 800 mg L-1) or iodophor (10, 50, 100 and 150 mg L-1), 1-4-days post-fertilization. Bactericidal effect of disinfection, survival to hatching, hatching success and larval abnormalities were assessed. Larval survival was recorded at 5-, 10- and 15-days post-hatch (dph). Although Baltic cod eggs have an unusually thin chorion, they could tolerate surface disinfection. A reduction in bacterial growth was observed with increased concentrations of disinfectant (3.0 x 107-1.6 x 101 CFU mL-1). Abnormalities in newly hatched larvae were not related to disinfection. Survival of the yolk sac larvae was significantly better for eggs treated with 400 mg L-1 glutaraldehyde for 10 min at 10 and 15 dph. Effective disinfection was also recorded using 100 mg L-1 Actomar K30. Egg batch effect rather than initial bacterial concentration, disinfectant type or incubation method determined the survival of the eggs to hatching and survival of larvae. Because of the carcinogenic effect of glutaraldehyde, iodophor is recommended for routine disinfection of cod eggs.