Canadian Atlantic Oyster Drills (Urosalpinx) — Distribution and Industrial Importance
Distribution of drills (Urosalpinx cinerea Say) was worked out from critical examination of museum holdings, from assessment of published and several unpublished occurrence records, and from field collection in new areas. Drills occur in warm inlets on the Nova Scotia coast of the Bay of Fundy, possibly in one inlet of the outer Atlantic coast of Nova Scotia, and in several inlets of the southwestern Gulf of St. Lawrence. Only in the last were oysters found with the drills and there is only one record of serious damage to young oysters. Distribution patterns suggest that drills reached the Gulf of St. Lawrence by spreading eastward from Cape Cod, through the Bay of Fundy, then through a channel that is believed to have connected the Bay and the Gulf. There is no evidence of long-term restriction of distributional range since that pioneering period, but local distribution seems to have contracted so that now drills occupy only the warmest parts of their range. In the last 30 years, drill abundance in some important oyster-producing sections of the Gulf of St. Lawrence has decreased, perhaps because of low sea temperatures. Old colonies persist but do little damage in oyster areas. No new colonies seem to have sprung up. In our area the species seems to be bordering on extinction. Drills are not a threat to the Canadian east-coast oyster industry.