Spat Collection of a Non-Native Bivalve Species (European Oyster, Ostrea edulis) off the Eastern Canadian Coast

Abstract

A European oyster population (Ostrea edulis) was recently discovered off the Eastern coast of Canada. The occurrence of this population led various aquaculture stakeholders to consider this species commercially. The aim of this study is to determine the best time to collect the European oyster larvae to maximize their collection. Gonad observations and plankton tows were carried out in 2005 and 2006 to estimate the time of settlement. Nine days after the first free-swimming larvae were observed, Chinese hat collectors were suspended in the water column every three days at two sites. The collectors were removed from the water after a mean streaming duration of 35 days. Spat were thereafter numbered on each collector. The spawning period lasted from mid-July to the end of August in 2005 and from mid-July to the beginning of August in 2006. Temperature was approximately 18°C during that time. The major peaks of free-swimming larvae were observed at the beginning of August (43,276 larvae m−3) in 2005 and at the end of July (224,322 larvae m−3) in 2006. Spat numbers were higher in 2005 (22,791 spat collector−1) than in 2006 (124 spat collector−1). The lower spat collection in 2006 might be related to nonfavorable environmental conditions observed during that summer. Salinity, in 2006, varied from 18‰ to 30‰ compared with 25‰ to 30‰ in 2005. Spawning in Eastern Canada is apparently occurring at a higher temperature (18°C) compare with other populations around the world (13°C to 16°C). This difference may be related to several factors such as the geographical location and food availability.