抄録
Abstract: Recruitment of naturally occurring Japanese scallops(Patinopecten(Mizuhopecten)yessoensis)into sowing-culture grounds has important implications for the population dynamics and aquaculture man agement because it can cause unfavorable lower growth due to high density and a highly variable size range, which can lead to increased costs for harvesting and selecting market-sized scallops. In the present study, the occurrence and magnitude of natural recruitment in a scallop population cultivated at Yubetsu seabed(northern Japan)was investigated. Assessment was done through a photocensus at 4 culture areas, A, B, C and D, which contained 1-, 2-, 3- and 4-year classes of seeded scallops, respectively. The magnitude of natural recruitment varied annually among the culture areas. In 1990 and 1991, natural recruits composed 20 and 32% of the scallops in area C and B, respectively. In 1992, few natural recruits were observed in area A(8%)and C(7%). The highest number of natural recruits occurred in 1993 in area A(≥ 41%). These results suggest that routine monitoring of density throughout the whole period of culture is indispensable. Transfer of scallops from high-density areas caused by natural recruitment to low-density areas should be considered.
