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Management of husbandry practices to maintain water column environmental carrying capacity for bivalve culture



Related project: PARR-2011-G-04

Bivalves have an extraordinary filtration capacity that enables them to extract suspended food particles from the water column. Densely stocked bivalves can deplete available food particles faster than can be replaced through primary production and water renewal. Both industry and regulatory agencies recognize the need to identify the stocking density at which the demand for food particles is well matched to the supply.

Simple standards and elaborate numerical models have been developed, but there are knowledge gaps such as the influence of husbandry (farm management) practices on the time it takes a population of cultivated bivalves to filter a body of water. This project furthered the development of carrying capacity indicators for longline mussel farming areas by integrating husbandry practices (e.g., tunicate control) into model simulations and predictions.


The modeling of husbandry practices revealed that two invasive tunicates, Ciona intestinalis and Styela clava, can significantly increase the demand for phytoplankton in Prince Edward Island (PEI) mussel (Mytilus edulis) culture embayments. The magnitude of this impact was dependent on whether or not sleeves (mussel socks) were treated for these tunicates. In simulations where infested sleeves were not treated, phytoplankton uptake rose by 150 to 171 percent above non-infested outcomes.

In parallel feeding experiments mussels and tunicates competed for the large phytoplankton cells (nanophytoplankton), but only tunicates effectively consumed the smaller cells (picophytoplankton), which contributed to the bulk of the primary production in some PEI embayments. Mussels were nonetheless capable of assimilating picophytoplankton carbon, namely by ingesting feces and pseudofeces of filter-feeders growing in close proximity.

An elaborate hydrodynamic-biogeochemical model was developed to study St Peter's Bay, where 40 percent of the bay area is dedicated to mussel culture. Results suggest that the system is near its ultimate capacity, a state where the energy cycle is restricted to nitrogen-phytoplankton-detritus-mussels with few resources left to be transferred to higher trophic levels.

Finally, a climate change scenario (year 2050) predicted a 30 percent increase in mussel production, largely driven by more efficient utilization of the phytoplankton spring bloom. However, the predicted elevated summer temperatures (greater than 25 degrees Celsius) may also have deleterious physiological effects on mussels and possibly increase summer mortality levels. Climate change may lead to increases in production and ecological carrying capacity as long as the cultivated species can tolerate warmer summer conditions.


Comeau, L.A., Filgueira, R., Guyondet, T., Sonier, R. 2015. The impact of invasive tunicates on the demand for phytoplankton in longline mussel farms. Aquaculture 441 :95–105.
Guyondet, T., Comeau, L.A., Bacher, C., Grant, J., Rosland, R., Sonier, R., Filgueira, R. 2015. Climate change influences carrying capacity in a coastal embayment dedicated to shellfish aquaculture. Estuar. Coast. 38 :1593-1618.
Sonier, R. 2017. Rôle nutritionnel du picophytoplancton pour les bivalves d’élevage. Ph.D. thesis. Université du Québec à Rimouski.
Sonier, R., Filgueira, R., Guyondet, T., Tremblay, R., Olivier, F., Meziane, T., Starr, M., LeBlanc, A.R., Comeau, L.A. 2016. Picophytoplankton contribution to Mytilus edulis growth in an intensive culture environment. Mar. Biol. 163:1–15.
Sonier, R., Comeau, L.A., Tremblay, R., Olivier, F., Meziane, T., Genard, B. 2020. Mytilus edulis and Styela clava assimilate picophytoplankton carbon through feces and pseudofeces ingestion. Aquaculture 531:735868.

Program Name

Program for Aquaculture Regulatory Research (PARR)


2010 - 2013

Principal Investigator(s)

Luc Comeau, Research Scientist, Fisheries and Oceans Canada, Gulf Fisheries Centre, Gulf Region

Team Member(s)

Michel Starr, Fisheries and Oceans Canada, Institut Maurice-Lamontagne, Québec Region

Liliane St-Amand, Fisheries and Oceans Canada, Institut Maurice-Lamontagne, Québec Region

Thomas Guyondet, Fisheries and Oceans Canada, Gulf Fisheries Centre, Gulf Region

Rémi Sonier, Fisheries and Oceans Canada, Gulf Fisheries Centre, Gulf Region

Chris McKindsey, Fisheries and Oceans Canada, Institut Maurice-Lamontagne, Québec Region

Réjean Tremblay, Institut des sciences de la mer

Jon Grant, Dalhousie University

Ramon Filgueira, Dalhousie University

Rune Rosland, University of Bergen

Cédric Bacher, Institut français de recherche pour l'exploitation de la mer (Ifremer), France

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