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Identifying critical ecological thresholds for tunicate infestations on mussel farms



Bio-fouling is a well documented shellfish aquaculture industry challenge and the recent introduction of several invasive tunicate species has greatly inflated its impact. The PEI mussel aquaculture industry has been particularly affected by the introduction of four new tunicate species: Clubbed Tunicate (Ciona intestinalis) in 1998 in the eastern end of the province; Golden Star Tunicate (Ciona intestinalis) in 2001 and 2002 and Violet Tunicate (Ciona intestinalis) were both reported on the north coast of PEI; and in 2004, the Vase Tunicate (Ciona intestinalis) was first reported on the east coast of the island. Efforts to control the spread of these tunicate species have been relatively successful, but presently most mussel producing areas in PEI are infested with at least one tunicate species. Currently, high pressure water spray is the main technique used by the mussel industry to control tunicate fouling. Lime dipping is also used to control tunicates, particularly the Clubbed Tunicate, on mussel socks. Efforts to develop the most cost-effective treatment strategy are continuing while specific ecological thresholds are not yet established. The establishment of both economical and ecological thresholds are key to the sustainability of the mussel industry in PEI and could lead to the creation of the first Integrated Pest Management approach for Aquatic Invasive Species. The goal of this project is to investigate the ecological impact of tunicate treatment with the following objectives:

  1. develop a method to estimate the tunicate biomass on mussel farm structures;
  2. develop a model to predict the impact of tunicates fall-off, pre- and post-treatment, on the benthic environment; and
  3. assess the impact of tunicate filtration and biodeposition on ecosystem productivity.

Results from this project will also provide information on timing and coordination of treatment.





Program Name

Program for Aquaculture Regulatory Research (PARR)


2011 - 2014


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

Principal Investigator(s)

Thomas Landry
343 Ave Université Ave, Moncton, NB
Tel.: (506) 851-6219

Team Member(s)

Andrea Locke, DFO-Gulf region

Chris McKindsey, DFO-Québec region

Aaron Ramsay, DFARD-PE;

Monique Niles, DFO-Gulf region

Daniel Bourque, DFO-Gulf region

Thomas Guyondet, DFO-Gulf region

Luc Comeau, DFO-Gulf region

Jeff Davidson, AVC-UPEI

Thitiwan Patanastienkul, AVC-PEI

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