Influence of Eastern Oyster (Crassostrea virginica) aquaculture overwintering on eelgrass (Zostera marina)



Eelgrass (Zostera marina) provides fish habitat to numerous commercial fish species and is considered an Ecologically Significant Species (ESS) in Atlantic Canada. There are concerns that various activities related to oyster aquaculture are causing disturbance and alteration to eelgrass beds. One such practice, which occurs in the southern Gulf of St. Lawrence, is the benthic over-wintering of oyster bags. During the open water seasons, oysters are cultured in plastic mesh bags attached to long lines floated at the water surface. However, in this area where surface waters typically freeze, the bags are moved to the deepest part of the lease and dropped to the bottom where they can be left to overwinter or accessed through the ice for harvesting. Since the substrate of these lease areas is often characterized by eelgrass habitat, concern has been expressed by habitat regulators about physical damage that may be caused to eelgrass by these over-wintering activities.

This project is designed to assess the potential impact that the practice of overwintering oyster bags may have on eelgrass beds in the southern Gulf of St. Lawrence and will provide the opportunity to study eelgrass winter ecology and its susceptibility to disturbance during this period. The project will also examine the environmental performance of a newly developed bivalve aquaculture technology (Horizontal Rope Floating Rack system). This floating rack system rests on the substrate while ensuring the oysters themselves do not make contact with the benthos. We hypothesize this system will cause less benthic disturbance than current culture structures while also lessening oyster mortality. The results of this study are expected to contribute to scientific advice for regulatory decisions and best management practices to minimize and/or mitigate potential negative impacts of oyster aquaculture on eelgrass habitat.





Program Name

Program for Aquaculture Regulatory Research (PARR)


2012 - 2014


Atlantic: Gulf of St. Lawrence, St. Lawrence Estuary

Principal Investigator(s)

Simon Courtenay
Research Scientist, Fisheries and Oceans Canada at the Canadian Rivers Institute, Department of Biology, University of New Brunswick
P.O. Box 4400, 10 Bailey Drive, Fredericton, New Brunswick, E3B 5A3
Tel.: (506) 452-6212
Fax: (506) 453-3583

Team Member(s)

Ms. Monica Boudreau, DFO-Gulf Region

Mr. Marc Skinner, Stantec Consulting Ltd./ Canadian Rivers Institute

Collaborative Partner(s)

Dr. André L. Mallet (President, L'Étang Ruisseau Bar Lté e)