Effects of egg disinfection and incubation temperature on early life stages of spotted wolffish

Eggs of spotted wolffish (Anarhichas minor Olafsen) were incubated at constant 4, 6 and 8 degreesC, and disinfected with glutaric dialdehyde (150 p. p. m. for 5 min) once or twice a month during two thirds of the incubation period, to prevent growth of microorganisms. Hatching of apparently normal larvae started earlier when eggs were disinfected twice a month compared to once a month at all incubation temperature regimes. The time to 50% hatch was 900 and 920 day-degrees (16 and 16,5 weeks) at 8 degreesC, 835 and 880 day-degrees (20 and 21 weeks) at 6 degreesC and 725 and 800 day-degrees (26 and 28,5 weeks) at 4 degreesC, in the egg groups disinfected twice or once a month, respectively. The best survival until hatching was noted when eggs were disinfected twice a month and incubated at 6 and 8 degreesC. Survival was very low at 4 degreesC. Prematurely hatched larvae were registered in all egg groups disinfected twice a month and the highest frequency was noted in the 8 degreesC groups. The larval weight at normal hatching in the 6 and 8 degreesC groups was negatively correlated with incubation temperature and intervals of disinfection during the incubation period, but after 42 days feeding with live feed (unenriched Artemia) the weights of the larvae were not significantly different. The specific growth rates of the larvae from the eggs incubated at 6 degreesC and 8 degreesC were 3.0% and 3.2%, respectively. The mean survival of larvae was between 88% and 96% at 42 days post-hatching. Young wolffish originating from the 6 degreesC incubation groups showed lowest mortality.