MEPS 513:17-27 (2014)  -  DOI: https://doi.org/10.3354/meps10989

ABSTRACT: Annual recruitment of bivalves in the Wadden Sea is usually more successful in summers after cold than after mild winters. The new generation (0-group) of the main predators (shrimps and shore crabs) of early benthic stages of bivalves appear later in spring on tidal flats after colder winters. If these predators were more retarded by low water temperatures than their prey, the bivalve post-larvae would profit from a head start, enabling them to outgrow most predators and generate a strong new year-class. To test this hypothesis, we present a data series on bivalve post-larval density and 0-group shrimp and shore crab biomass in April to July of 10 to 30 yr in a tidal flat of the western Wadden Sea. With lower preceding winter water temperature, post-larvae of the bivalves Macoma balthica, Cerastoderma edule, and Mya arenaria and members of 0-group shrimp Crangon crangon and shore crab Carcinus maenas arrived later in spring, but only crabs responded much stronger to water temperatures than their prey did. Among the bivalves, post-larvae of M. balthica were the first to arrive and C. edule the last. Among the 0-group predators, shrimps arrived in April/May and shore crabs in June/July. Shrimp were present simultaneously with tiny just-settled bivalve post-larvae after cold and mild winters, whereas juvenile crabs were usually too late to seriously affect the abundance of the earliest bivalve prey. For most of spring, predation by crabs was limited to prey consumption by older crabs. Late-summer recruit numbers could be predicted within 1 or 2 mo after the start of their settlement, indicating that critical interactions occurred when they were very small. We conclude that there is limited evidence for possible mismatches in timing of interactions between just-settled bivalve post-larvae and their epibenthic predators as an explanation for the generally higher recruitment success in bivalves after severe winters.

KEY WORDS: Seasonal timing · Water temperature · Tidal flats · Wadden Sea · Macoma balthica · Cerastoderma edule · Mya arenaria · Crangon crangon · Carcinus maenas