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Health status update of Mercenaria mercenaria in St-Mary’s Bay, Nova Scotia



With the rise of climate change, many pathogens have changed or expanded their distribution ranges where they have become invaders of new ecosystems and have the potential to cause high mortality rates. Understanding shellfish habitat and how shellfish are vulnerable to climate-related change are  necessary for better understanding the effects of climate change and the implications on shellfish aquaculture. This project revisited the health status of the Quahog (Mercenaria mercenaria), environmental conditions in St-Mary’s Bay, and added measures pertaining to shell condition. The objectives of this project were to:

  1. Revisit the health status of the Quahog (M. mercenaria) and environmental conditions in St-Mary’s Bay
  2. Add measures pertaining to shell condition (structure and composition)
  3. Measure calcium carbonate (aragonite) availability of which this organism is dependent upon
  4. Compare health and shell conditions between sites within the sampling area.

Improving the knowledge base about diseases and other climate change stressors is important for future monitoring of this ecologically and economically important area, and for mitigation purposes.


No notable differences were seen between recent (2017-2018) and past (2005-2007) health assessments, and no emerging diseases were observed in the updated health analysis. No report of Quahog mortalities were issued during the time between both studies.
Shell hardness was measured and baseline data were established for St-Mary’s Bay. The data could not be compared as shell hardness was not measured previously in this area. However, these data can be used as a reference for future shell hardness measurements in St-Mary’s Bay. As expected, the temperature trend shows a lowering in temperature as the year advances. The salinity and pH values remain stable throughout.

Analysis of scanning electron microscopy (SEM) images revealed shell damage. However, it was unclear if the damage was from sample manipulation, naturally occurring, or resulted from acidification.

Additional time and sampling is required to fully understand the impact of climate change on Quahogs in St-Mary’s Bay. This study does provide baseline and updated data for future studies. The data gathered could help mitigate the impact of changes in the environment, either natural or anthropogenic, by adapting or changing aquaculture techniques, practices or locations.

Program name

Aquaculture Collaborative Research and Development Program (ACRDP)


2017 – 2019

Principal investigator

Michelle Maillet, Biologist, Fisheries and Oceans Canada, Gulf Fisheries Center, Gulf Region

Team member(s)

Kadra Benhalima, Biologist, Fisheries and Oceans Canada, Gulf Fisheries Center, Gulf Region


Doug Bertram, Innovative Fisheries Products Inc.

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