VULNERABILITY OF LATE LARVAL AND EARLY JUVENILE ATLANTIC HERRING, CLUPEA-HARENGUS, TO PREDATION BY WHITING, MERLANGIUS-MERLANGUS

Laboratory experiments investigated changes in the vulnerability of he rring to predation by whiting during growth from <34 to >80 mm in leng th. Premetamorphic herring (<50 mm) failed to react to c. 50% of attac ks by the predator, but this was reduced to c. 20% in postmetamorphic fish. Premetamorphic herring failing to react had c. 30% probability o f survival due to unforced errors by the predator (unsuccessful attack s that did not elicit a reaction by the prey) but these errors did not occur after herring metamorphosis. The loss of the advantage of lower conspicuousness following metamorphosis was counterbalanced by increa sed reactivity. Antipredator benefits should increase with schooling b ehaviour (first evident in experiments at c. 50 mm), so predation mort ality should decrease in postmetamorphic herring in the sea. Metamorph osis itself would be associated with high predation risk since conspic uousness is enhanced but reactivity and schooling behaviour are still not fully developed.