On Monday and Tuesday, 15 floating docks were removed from Foxtrap harbour to deal with an invasive aquatic species believed to have come from Placentia Bay.
Golden star tunicate are small aquatic animals with a sac-like body. Protected by a layer like a coat (or tunic), they live in groups and feed by filtering sea water through their bodies. Despite their name, golden star tunicate vary in colour.
The Department of Fisheries and Oceans (DFO) has been conducting invasive species surveys on tunicate since 2006.
Cynthia McKenzie, a research scientist with DFO’s science branch, is the lead scientist on the surveys.
She said golden star tunicate were first discovered in Argentia as part of a survey that same year and have since been found in several other locations within Placentia Bay.
Golden star tunicate can prove particularly harmful to aquaculture, McKenzie said.
As they form colonies, sometimes up to 10 centimetres in diameter, the tunicate form a carpet that suffocates everything around it. It can also attach to boats in the water, helping tunicate travel to other regions.
In the Maritimes, carpet-forming or colonial tunicate have attached to the mussel lines used for aquaculture operations, interfering with their growth and increasing the cost of processing them as a result.
Mussels and scallops, like tunicate, are filter feeders.
“This is one of the reasons we’re particularly interested in making sure it doesn’t spread around the province, because it will have an impact on a lot of things,” McKenzie said.
The issue was first identified in Foxtrap by divers collecting kelp. The divers had previously worked on invasive species surveys with McKenzie and were able to identify the golden star tunicate.
McKenzie said once it was determined tunicate were restricted to floating docks, the option to remove the docks became a simple solution for the problem.
“Once they’re in the air, they die pretty quickly,” she said. “We’re actually hoping this will stop an invasion from moving into Conception Bay.”
She said tunicate on the floating docks had spread more rapidly than in Arnold’s Cove, where scientists have been conducting surveys for three years.
McKenzie is uncertain why that was the case, but she said graduate students from Memorial University are conducting genetic work on samples from the harbour that may offer some clues.
Most golden star tunicate found on the docks were in the early stages of development. McKenzie said as an invasive species, golden star tunicate do not have many natural predators.
To help prevent invasive tunicate from spreading, she said fish harvesters can play a role by learning to identify them.
“They’re actually quite easy to identify. The people we were working with in Foxtrap harbour, we showed them exactly what they look like, and now they’re aware of it, and they’re going to keep an eye on them.”
She said Newfoundland and Labrador benefits from the fact most boat owners remove their vessels from water once the fishing season concludes. This, combined with cool water temperatures, helps prevent invasive species from flourishing.
If a boater spots golden star tunicate on their hull, McKenzie advises them to scrape it off and dump the tunicate on dry land to let it die.
The floating docks will remain on land over the winter and be returned to the harbour in the spring.
There are many types of tunicate in existence, some of which are native to this province rather than being invasive. It was for this reason the science branch of DFO launched its tunicate surveys.
Work on the floating docks was jointly performed by DFO’s science branch, Memorial University’s Ocean Sciences Centre, and DFO’s Small Craft Harbours program.