Predation Impact of Small Drilling Gastropods on the Japanese ScallopMizuhopecten yessoensis

Abstract

ABSTRACT Although the Japanese scallop Mizuhopecten yessoensis is the variety used in the largest production of scallops in the world, knowledge about its predators is very limited, and gastropods have not generally been recognized as a predator. This study demonstrates the impact of predatory gastropods on the Japanese scallop through a field survey and laboratory experiments. The 4-y field survey at a lagoon in northern Japan demonstrated that the frequency of scallops that have boreholes on their shells represented 11.3%–73.8% of dead individuals at 3 y old (shell height, >90 mm) that would have been harvested 7 mo later. By calculating the natural mortality of scallops after their release on the sowing—culture grounds in the lagoon, we estimated that 17.8% of the released scallops were attacked by drilling animals. This estimation, however, probably underestimates the impact of drilling predators, because the drilling frequency on small (young) individuals (shell height, <55 mm) was 10 times greater t...