Larval supply of predator and prey: temporal mismatch between crabs and bivalves after a severe winter in the Wadden Sea

Enhanced bivalve recruitment after severe winters is a well-known phenomenon in the coastal North Sea. By comparing the bivalve larval abundances in the northern Wadden Sea after a severe (1995/96), a moderate (1996/97) and a mild (1997/98) winter we found no evidence for the hypothesis that high bivalve recruitment after severe winters is caused by enhanced larval supply. Total and peak abundances of all bivalve larvae as well as of each of four separate species Ensis americanus, Mytilus edulis, Cerastoderma edule and Mya arenaria were three to six times lower after the severe than after the mild winter. In Macoma balthica total and peak abundances after the severe winter were only slightly higher than after the moderate winter. The larvae of the epibenthic predator Carcinus maenas appeared in lower numbers and six to eight weeks later after the severe winter than after the moderate and the mild winter. Since the bivalve larvae appeared without, or with less, delay after the severe winter, there was a temporal mismatch between Carcinus and the bivalves, supporting the hypothesis that reduced epibenthic predation is an important factor in high bivalve recruitment after severe winters.