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CONTEXT
Invasive tunicates or ‘sea squirts’ are a type of aquatic invasive species (AIS), which pose a serious threat to the environment, economy or society. When AIS become established in a new habitat, they can exert serious ecologic and economic effects on the ecosystem.
The Clubbed tunicate, Styela clava, was the first invasive tunicate species introduced into PEI waters in 1998. More recently, the colonial tunicates Botrylloides violaceus, (Violet tunicate), and Botryllus schlosseri, (Star tunicate), have been observed.
The violet tunicate and golden star tunicate, unlike the solitary clubbed tunicate, are colonial and thus considered a greater fouling challenge for the mussel industry. They not only reproduce sexually spreading larvae through the water column but also can bud or fragment, producing new colonies which will drift and easily spread the tunicate further out into the bay or estuary.
The violet tunicate has been established in Savage Harbour since at least the summer of 2004, and has been recently reported in other PEI bays, including Cardigan River which is in close proximity to three other important mussel culture systems (Brudenell River, Montague River and St. Mary’s Bay). The estimated landed value of mussel crop in these waters is approximately $10, million annually.
RESEARCH PROJECT
At the present time, there are no established rapid response measures to treat these types of infestations. As part of the project, all infested farms in Cardigan River will be treated in order to reduce the biomass of violet tunicates on mussel socks and culture gear.
The effect of this rapid response will be evaluated and compared to the treatment levels in Cardigan Bay by using Savage Harbour as a control bay. A secondary objective will be to monitor the effect of treatment on the infestation levels both on the mussel groupings (socks) and the bottom under and around the infested farms.
The information and expertise generated from this project will assist in the development of rational management strategies for industry and government.
This is a joint venture with DFO ($140,000), the Province of Prince Edward Island ($60,000), and the Prince Edward Island Aquaculture Alliance (in dollars and in kind). The funding is provided under the Aquaculture Collaborative Research and Development Program (ACRDP) (Canada) and the Aquaculture and Fisheries Research Initiative (AFRI) (PEI). The purpose of the project is to identify avoidance strategies and husbandry methods to control fouling and predators. This project will also tie into research that is already being conducted collaboratively through the Invasive Tunicate Research Action Team and the Case Study of Tunicates in Maritime Canada.
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