Occurrence and detrimental effects of the bivalve-inhabiting hydroid on juveniles of the Japanese scallop in Funka Bay, Japan: relationship to juvenile massive mortality in 2003.

In November 2003, we first observed prevalent occurrence of a hydroid, , on soft body tissues of age zero Japanese scallop () juveniles cultured in large areas of Funka Bay, Hokkaido. The occurrence coincided with massive death of juvenile scallops. A major objective was to clarify ecological relationships between the symbionts, and to infer the relationship between symbiosis and the massive mortality.