Scientific research on tunicates

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Science is the key to an economically and environmentally sustainable aquaculture industry. Fisheries and Oceans Canada scientists and researchers have worked to build understanding and knowledge about tunicates and other aquatic invasive species, including the treatments and control methods used to reduce their presence and impact on Canada’s shellfish aquaculture operations.

Detection, prevention and treatment

More than 20 individual projects were conducted between 2007 and 2008 to reduce the impact of invasive tunicates on mussel crops and to improve productivity in infested waters using innovative equipment and approaches. As a result, treatment techniques and strategies to mitigate the impact of aquatic invasive species were developed and are used by industry along with other control measures.

  • Canadian Aquaculture R&D Review articles: 2009, 2011
  • Fact sheet: Containment and mitigation of nuisance tunicates on Prince Edward Island to improve mussel farm productivity

A four-year research initiative was also undertaken in PEI to address tunicates at three different levels: detection, prevention, and treatment. Researchers sought to develop a diagnostic kit using genetic material to identify different tunicate life stages in sea water samples as part of the detection component of the study. For the prevention component, the team analyzed marine samples to develop an environmentally sound and sustainable anti-fouling agent derived from marine natural products. The work on different tunicate treatments involved field work and direct collaboration with industry to develop new treatments for the mitigation of tunicates.

  • Canadian Aquaculture R&D Review article: 2009

Equipment designed to mitigate the impact of solitary and colonial tunicate species on mussel farms was developed and evaluated over a one-year period. As a result, two innovative systems to treat colonial tunicates in and out of the water are now available.

The risk of spreading tunicates through husbandry practices and environmental conditions within processing plants was evaluated in order to identify processing stages that present a high risk of introduction of the invasive species. Secondly, research sought to develop control strategies to minimize the potential for gamete and larvae tunicate releases.

  • Canadian Aquaculture R&D Review article: 2007

Violet tunicate-invested farms in Prince Edward Island’s Cardigan River were treated in order to reduce the biomass of the tunicates on mussel socks and culture gear. The effect of the treatment was evaluated and compared using Savage Harbour as a control bay. The effect of treatment on the infestation levels was also monitored on the socks and the bottom under and around infested farms. The project sought to identify avoidance strategies and husbandry methods to control fouling and predators.

  • Canadian Aquaculture R&D Review article: 2007

Between 2009 and 2001, research was undertaken in British Columbia to assess the efficacy of various mechanical (scrubbing), biological (sea urchin grazing), and chemical (lime, acetic acid, bring, fresh water) means of tunicate control in Pacific oyster culture.

  • Canadian Aquaculture R&D Review article:  2011

Risks associated with species transfers – Industry and Governments are looking at ways to help set appropriate processes and regulations on transfers of aquaculture species from one area to another without risking potential introductions of invasive species (such as tunicates) into receiving environments.

  • Canadian Aquaculture R&D Review article: 2011

Biology

From 2008 to 2011, research was undertaken to explore how some aspects of C. intestinalis tunicate biology could be exploited using passive approaches to minimize tunicate abundance in aquaculture sites. Specifically, the study sought to determine the optimal time and effort of active treatment by investigating the reproductive biology of the tunicate species and to evaluate environmental tolerances of tunicate early-life stages in terms of their level of vulnerability to natural and/or treatment conditions.

Researchers in Nova Scotia set out to better understand the distribution and biology of the five species of tunicate found in the Province in order to facilitate the development of an effective management strategy against the invasive species.

Researchers in British Columbia investigated how changes in environmental conditions (e.g., temperature, salinity, etc.), predation intensity, and physical/chemical treatments affected the survivorship, growth, and reproduction of four species of tunicates. The results were expected to provide information on the ability of tunicates to invade new habitats in BC waters.

Impact on shellfish and/or the marine environment

Researchers in Prince Edward Island are undertaking a two year project to identify the critical ecological thresholds for tunicate infestation on mussel farms. The establishment of both economical and ecological thresholds is central to the sustainability of the mussel industry in PEI.

Experimental mussel sock with tunicates over sediment trap
Experimental mussel sock with tunicates over sediment trap

Between 2008 and 2009, researchers assessed the influence of mussels and/or associated tunicates on plankton community size and structure in PEI to improve understanding of the interactions between farmed mussels and tunicates, as well as their impacts on planktonic communities.

  • Canadian Aquaculture R&D Review article: 2009

To predict benthic loading within a culture site, small mussel socks with and without two species of tunicates and control socks were constructed to evaluate sedimentation rates associated with mussels and fouling organisms in field conditions. The research indicated that benthic loading was much greater, although more restrained spatially, when tunicates are present.

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