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The effect of cultured shellfish on eelgrass productivity in estuaries of New Brunswick and Prince Edward Island



In natural systems, shellfish affect the abundance of plankton in the water column, and as a result, may affect the diversity, productivity, and the community structure of the food chain (Canadian Science Advisory Secretariat Science Advisory Report - CSAS-SAR 2006/005). The coexistence of cultured and wild stocks of American Oyster and Blue Mussels makes it difficult to distinguish between the effects of cultured and wild shellfish on the ecosystem. The complex nature of interactions in the coastal zone between farmed and wild shellfish, and nutrient cycling, can further obscure the net effects of shellfish aquaculture. Environmental effects of shellfish aquaculture in eastern Canada on eelgrass and its function as fish habitat are associated with sedimentation, turbidity/shading, nutrients, flow patterns, and physical damage or removal. Shading from oyster aquaculture gear has been associated with a reduction in eelgrass productivity at a local scale. However, there is a knowledge gap related to the potential offsetting effects of cultured shellfish biomass in improving the overall eelgrass productivity by influencing bay scale turbidity patterns.

This study is investigating the effects of cultured shellfish on eelgrass productivity at the bay scale. This will be achieved through field studies that describe the landscape and seascapes of four cultured bays with a focus on shellfish populations (wild and cultured) and eelgrass beds. A laboratory study will evaluate the rates at which mussels and oysters filter water, and the resulting effect on turbidity (water clarity), seston (particles suspended in the water) and light attenuation. Modifications to the existing hydrodynamic models for the region will be implemented (Canadian Science Advisory Secretariat Science Advisory Report - CSAS-SAR2015/003) to include turbidity, sedimentation and re-suspension, and to incorporate the results of the lab-derived clearing rates of mussels and oysters, allowing for improved estimates of bay-scale effects from existing (or proposed) shellfish leases.





Program Name

Program for Aquaculture Regulatory Research (PARR)


2014 - 2017


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

Principal Investigator(s)

Marc Ouellette
Aquatic Science Biologist, Gulf Fisheries Centre, Science Branch
343 Université Avenue, Moncton, New Brunswick

Team Member(s)

Monique Niles

Thomas Guyondet

Thomas Landry

Collaborative Partner(s)

Tim Webster, AGRG-NSCC

Kate Collins, AGRG-NSCC

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