Plasma Antifreeze Levels Reflect the Migratory Behaviour of Atlantic Herring (Clupea harengus harengus) in the Southern Gulf of St. Lawrence

This study compared freeze protection conferred by blood antifreeze proteins to juvenile and adult Atlantic herring (Clupea harengus harengus) in the southern Gulf of St. Lawrence in December 1988. Juvenile herring had significantly lower plasma freezing points and significantly higher antifreeze activity than adults. Differences in antifreeze activity and in late autumn distribution suggest that juvenile herring are more capable of wintering in the Gulf of St. Lawrence than adults. This conclusion is consistent with our observation that during December, juveniles were present in shallow waters of Chaleur Bay, which is ice-covered during winter, while adults were found only in the deeper waters of Sydney Bight, which do not freeze during winter.