The vase tunicate has landed

DFO officials working on problem

Paul Herridge
Published on July 19, 2013

Floating docks in Little Bay were removed from the water, cleaned and left to dry last week as Department of Fisheries and Oceans scientists studied an invasive species, vase tunicate, attached to the community wharf. Paul Herridge Photo


A new and unwelcome visitor has turned up in Placentia Bay that could have devastating implications for the province’s shellfish aquaculture industry.

The ‘vase tunicate’ was discovered last September for the first time in the province in Burin.

According to Cynthia McKenzie, a research scientist with the Department of Fisheries and Oceans (DFO) in St. John’s, not only aquaculture farms, but the fishing industry in general will suffer if the species spreads unabated.

Following the Burin discovery, a resulting rapid assessment survey by DFO and Memorial University’s joint Aquatic Invasive Species monitoring team found the vase tunicate in large numbers around the wharf area in Little Bay, Marystown.

“We think it may have been here for about a year, based on the size of things and what people have said about how long they have seen things.”

Last week, Ms. McKenzie led an effort to combat the infestation and halt its progress.

“We’ve been doing surveys since 2006 for invasive species, and that’s how we’ve found various things like the violet tunicate in Belloram and golden star in different places.

“We took out the docks in Foxtrap two years ago when we found golden star in there. If you can take the dock out that’s definitely the way to go.”

Floating docks in Little Bay were removed from the water, cleaned and left to dry, while divers removed and collected the organisms from under the wharf.

Ms. McKenzie said the Department of Fisheries and Aquaculture was planning to bring in a high-pressure sprayer to see how well that would work.

With all having a vested interest, she acknowledged the federal and provincial governments as well as industry and academia were involved in the endeavour.

“Everybody has their own little piece of the effort.”

The vase tunicate, or Ciona intestinalis, has a cylindrical, unstalked and translucent body that can grow to about 15 centimetres in length. It varies in colour from light greenish-yellow to orange or pink.

Native to northern Europe, it develops individually, but can cluster together with other vase tunicates to form masses of clumps, weighing down and fouling fishing gear.

Ms. McKenzie described the vase tunicate as “a sack of water that reproduces and eats, and that’s it.”

She said it out competes all other filter feeders, like scallops and mussels, for food and completely takes over an area so nothing else grows there.

When water temperatures reach eight degrees Celsius, she indicated the vase tunicate will spawn again and again, noting the monitoring team observed the organisms reproducing as late as November last year in Little Bay.

Ms. McKenzie said the vase tunicate found in this area are most likely from another region of Atlantic Canada, where they are now large populations of the species. It’s close by, she noted, and there is a fair amount of movement back and forth.

The species also turned up in the French islands of St. Pierre and Miquelon last year.

Ms. McKenzie said genetic samples have been taken to compare with specimens from other areas of the world that will hopefully confirm the exact origins.

“They’re not going to likely go anywhere on their own. They are attached to a boat or gear and transported to another place. That’s how it works.”

Traditionally, Ms. McKenzie indicated boats owners in the province have regularly taken their vessels out of the water. Docks were regularly removed as well. With less ice these days, she said both are maybe not happening as frequently as they once did.

She said DFO has been trying to encourage boat owners to think about the importance of regularly cleaning their vessels as well as using anti-fouling paint to slow the growth of organisms that attach to the hull.

Hopefully, turning the tide against the vase tunicate will be less difficult than the violet tunicate, a variation of the species that was found in Belloram harbour in 2007. Ms. McKenzie said there is a key difference between the two.

Violet tunicate forms colonies, whereas the vase tunicates are singular organisms.

A wrapping technique was tried on the violet tunicate that was not as effective as it initially appeared. She noted simply scrapping it off, as with the vase tunicate, doesn’t work well either as any fragment can start a new colony on its own.

She said a research project is underway to look at how to use the violet tunicate’s own filtering system against them to suffocate the organism.

“We’re still in the process of trying to figure out how to do that.”

According to DFO’s website, there are several aquaculture licenses for blue mussels in Placentia Bay, mostly in and around the Merasheen Island area.

Ms. McKenzie suggested the additional cost of cleaning vase tunicates from aquaculture farm infrastructure would quite likely make the venture unviable.

“The people who own those leases (in Placentia Bay) know about it and are very aware of the problem. The aquaculture industry in general is very concerned.

“That’s one of the reasons all the stakeholders are really keen on trying to stop it here.”