THE INFLUENCE OF SALINITY ON THE MORPHOLOGICAL DEVELOPMENT OF YOLK-SAC LARVAE OF ATLANTIC HALIBUT, HIPPOGLOSSUS-HIPPOGLOSSUS (L.)

The effects of incubation salinity on survival and morphological devel opment of yolk sac larvae of Atlantic halibut, Hyppoglossus hippogloss us (L.), were studied at two salinities, 35.5 parts per thousand and 3 2.3 parts per thousand. Yolk sac larvae incubated at 35.5 parts per th ousand developed early tail deformities before 50 day-degrees (9 days posthatch), and necrosis, oedema and calculus in the urinary bladder a t about 150 day-degrees (28 days post-hatch). However, the incidence a nd severity of mouth deformity was not influenced by salinity, The cum ulative mortality up to first feeding was 17% when the larvae were inc ubated at 35.5 parts per thousand compared to 7% at 32.3 parts per tho usand. A broad variation between the different larval groups was noted in the extent of injuries induced by the higher salinity. Therefore, salinity must be considered as a critical environmental parameter for the yolk sac larvae of Atlantic halibut in aquaculture.