Interactions between predatory sea stars ( Asterias amurensis and Distolasterias nipon ) and Japanese scallops ( Mizuhopecten yessoensis ) and implications for scallop seeding in mariculture

Abstract

Sea stars are a key group of species in benthic marine ecosystems and represent the primary cause of mortality for cultured scallops. In the mariculture grounds of Japanese scallops (Mizuhopecten yessoensis) in north-eastern Japan, two sea star species, Asterias amurensis (AA) and Distolasterias nipon (DN), are serious predators. However, the predatory impact of these sea stars on scallops remains unquantified, with limited information being available on the biological characteristics of DN. We compared the predatory impact of both sea star species by evaluating their predatory behaviour (i.e. probability of predation and number of captured scallops) on scallops in laboratory experiments. Both sea star species preferred smaller scallops over large ones, with the probability of predation and the number of scallops being preyed on increasing with increasing water temperature. However, DN had a greater predation impact than AA. For instance, the probability of predation by DN was higher, with more scallops being consumed. In particular, compared to AA, DN continuously captured small scallops and fed on larger scallops. Furthermore, the predatory impact of both sea star species (particularly DN) on small scallops peaked at high temperatures. In conclusion, our results present information that could help improve the survival rate of seeded scallops in mariculture systems.