Miyagi Prefecture Fisheries Technology Institute, Ishinomaki, Miyagi 986-2135, Japan
In Miyagi Prefecture, the moon snail Euspira fortunei seems to have been brought from other prefectures or countries such as China or North Korea together with seeds of the clam Ruditapes philippinarum. This species is a predatory gastropod that drills holes in the shell of a prey and causes severe of damage for the fishery of R. philippinarum. The drilled holes produced by predatory gastropods are uniquely preserved on the prey shells and represent important evidence on the behavior of predators. In this study, the drilled-hole diameters were significantly correlated with predator size. The author collected drilled shells of dead R. philippinarum of Mangokuura and Torinoumi in Miyagi Prefecture, and calculated the E. fortunei shell height using the relationship between the drilled-hole diameter and shell height of E. fortunei. The prey sizes were correlated with calculated predator sizes in both areas, and the highest frequency of the predator-prey coefficient of shell length of prey (mm)/calculated shell height of predator (mm), was 0.7-0.8. These results indicate size-selective predation of E. fortunei.