Reproduction and depletion of the Manila clam in Maizuru Bay, Sea of Japan

Abstract

Wed aimed to conrm the reproduction of Manila clam Ruditapes philippinarum in Maizuru Bay, and also determine the cause of their mortality. Using seedling collectors, we obtained 5 to 60 juveniles per collector, demonstrating that this species is reproducing in the bay. Depletion of clams in Maizuru Bay was investigated by setting clams on coastal area sea beds in the summer. Predation was found to be more eŠective in depleting clams than environmental factors. Laboratory experiments revealed that juveniles less than 5 mm in shell length were preyed upon by 6 out of 13 sh species, whereas Japanese rock crab preyed upon clams from juveniles to adults.