Effective Pretreatments of Spat-collectors for Induced Settlement of the Pacific Oyster, Crassostrea gigas

Abstract

The effects of pretreatment of scallop shell spat-collectors on oyster Crassostrea gigas larval settlement were studied. Spat-collectors were pretreated by immersion in 1 mM L-DOPA, filtered seawater, surface seawater, filtered seawater with oyster shells or live adult oysters for 4 days. An average of 84% spats were found on spat-collectors pretreated in seawater with the presence of live adult oysters after 3 days of the settlement experiment. This settlement-inducing effect was increased by extending the pretreatment period and by increasing the number of adult oysters. The settlement-inducing effect decreased considerably when such pretreated spat-collectors were soaked in hot (50°C) water and dried. The results of these experiments confirmed that the pretreatment with live adult oysters increased the ratio of larval settlement to spat-collectors, and enabled the setting period to be reduced. The pretreatment of spat-collectors with live adult oysters could be applied to the large-scale artificial setting of oyster larvae.