The results of a long-term study of vertical distribution of the two main fouling species on scallop collectors of Japanese design—Japanese scallop, Mizuhopecten (= Patinopecten) yessoensis, and Pacific mussel, Mytilus trossulus—installed along the Primorsky Krai coast, Sea of Japan (East Sea), are presented in this article. The mussel, associated with Japanese scallop, is in fact its food competitor, which reduces its survival and growth rates. Settlement of scallop larvae begins earlier in shallow waters, i.e. in areas, where upper horizons are wormed up faster. A significant similarity in vertical distribution of juvenile scallop between stations is observed. The positive correlation between depth and vertical distribution of juvenile scallop is recorded most frequently in years with a high water temperature in June; for mussel, this relationship is always negative. Both climatic characteristics of year and position of the station exert influence on the depth of the maximum abundance of the young of the studied mollusks. Exposing scallop collectors at the optimum horizon, 9.5–15 m, promotes increase in the abundance of M. yessoensis and reduction in the abundance of M. trossulus.

Japanese scallop, pacific mussel, vertical distribution of juveniles, climate