Genetic considerations in transfers and introductions of scallops

As the potential of scallop aquaculture becomes increasinglyrealised, transfers (movement within a species' range) andintroductions (movement outside a species' range) of scallops arebecoming more common. To predict the genetic consequences oftransfers, information on genetic differences between source andrecipient populations is vital. Morphological, allozyme and DNAbased data on genetic differentiation of scallop populations andscallop sub-species are presented and discussed. Otherconsiderations are the numbers of individuals transferred andwhether they are wild stock or hatchery product. Loss of geneticdiversity is difficult to avoid in hatchery conditions althoughthere are ecological advantages to using disease-free hatcheryseed. Mitochondrial DNA data indicating significant geneticconsequences of the introduction of Argopecten irradians fromthe USA to China are discussed and compared with data onPatinopecten yessoensis introduced from Japan to Canada.Potential risks and consequences of hybridisation should beexperimentally assessed before introductions of scallops arecarried out. Hybridisation is unpredictable and can lead to lossof genetic diversity or breakdown of co-adapted gene complexes.The use of sterile triploid scallops for introductions to avoid hybridisation and reduce ecological impact has merit butreversion to diploidy may occur.