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Monitoring variability of environmental factors impacting tunicate infestation on coastal shellfish farms in Nova Scotia



The establishment of the solitary vase tunicate (Ciona intestinalis), an invasive species in the waters of Nova Scotia and Prince Edward Island, has negatively impacted mussel farm productivity in these areas. Vase tunicates grow in dense groups on mussel ropes, nets and the mussels themselves. Aside from competing with mussels for space and potentially food, fouled gear is much more difficult to handle (during harvesting for example) and can result in crop losses. Tunicates must be removed following harvesting and in heavily fouled sites they must be removed at least once before harvest, which is both a time and resource-intensive process. Despite the various management techniques in use (e.g., pressure washing, brine dips, liming, UV treatment, electric shocks), once established, vase tunicates are sufficiently persistent that their presence has become a serious hindrance to the mussel industry, and in extreme cases has cost farmers their businesses. The spatial distribution of the vase tunicate is highly heterogeneous and could be the result of variation in environmental factors between sites.

This project will examine the effect of variability of environmental factors (e.g., salinity, temperature, pH, and water movement) on the establishment and proliferation of vase tunicates. Results from this study may suggest an environmental factor to be used as an indicator to assess aquaculture sites (either current or future proposed sites) for their risk of tunicate infestation and inform siting decisions made by the government. This study may also help reduce further spread of this invasive species and the need for control treatments through the identification of sites less vulnerable to tunicate infestation.

This project supports the environmental performance objective of the Aquaculture Collaborative Research and Development Program (ACRDP), pertaining to the 2013-14 national ACRDP priority to evaluate the impact of the environment on shellfish aquaculture operations through the increase of the knowledge and understanding of how aquaculture shellfish operations interact with the environment.

Program Name

Aquaculture Collaborative Research and Development Program (ACRDP)


2013 - 2015


Atlantic: Gulf of Maine, Scotian Shelf

Principal Investigator(s)

Dawn Sephton

Collaborative Partner(s)

Aquaculture Association of Nova Scotia

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