Effects of sea star and crab predators on sea scallop (Placopectenmagellanicus) recruitment in the Mid-Atlantic Bight (USA)

摘要

This study investigated the spatial distribution and potential mortality on juvenile sea scallops (Placopecten magellanicus) in the Mid-Atlantic Bight imposed by three potential predator groups: the sand star Astropecten americanus, the common sea stars Asterias vulgaris and A. forbesi, and by the crabs Cancer irroratus and C. borealis. Both asteroid groups appear to reduce sea scallop recruitment, with significantly lower recruitment in areas where the sea stars were in high abundance. However, no significant effect of Cancer crabs on scallop recruitment was detected.A. americanus was most common in deep water (>75 m), Asterias in shallow water (27-40 m), while P. magellanicus was most common at intermediate depths (50-70 m). Very high densities of A. americanus, no sea scallop recruitment, and low Asterias densities were observed in all stations with depth greater than 85 m, and in many stations between 65-85 m. A. americanus may be an unusual type of "keystone" predator that is capable of excluding sea scallops and perhaps other prey species by direct consumption of newly settled spat, and may be excluding Asterias by competition and/or predation on its juveniles.