‘Sea squirts’ muscling in on Nova Scotia waters, including Halifax harbour

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By Haley Ryan - Metro Halifax

HALIFAX - The next time you take your boat for a spin in the Halifax harbour, or jump off the dock of a nearby lake, be sure to check underneath for “unwanted visitors,” says a biologist with the Department of Fisheries and Oceans.

Biologist Dawn Sephton said tunicates compete with shellfish for food, and weigh down fishing gear or buoys.

On Tuesday, workers at the Bedford Institute of Oceanography displayed different examples of foreign “sea squirts” or tunicates that have been found in the area.

Biologist Dawn Sephton said tunicates, which are cylindrical and look like large slugs, affect biodiversity, compete with shellfish for food, and weigh down fishing gear or buoys.

“(They’re) having a very direct and serious impact on the shellfish culture industry,” Sephton said about the vase and clubbed tunicate species, who have no predators here.

Sephton said the department tracks invasive species with 60 to 70 stations around the province and HRM, made up of six “collectors” or long strings dangling plastic plates.

The stations are checked in August and October, and depending on how “heavily fouled” the plates are with organisms, the department creates distribution maps for the province.

Now that regulations are in the works for aquatic species, Sephton said they will try to pinpoint the cost of these species to the fishing industry.

In 2012, three new types were detected in Nova Scotia: the European tunicate, diplosoma, and clubbed tunicate which is native to Korea and impacted P.E.I’s mussel industry, Sephton said.

“Last summer was an incredibly warm summer … and when the water’s warm it creates a new niche that some of these tropical species can exploit,” Sephton.

Green crabs are also a problem because they’re very aggressive and attack fish as well as harm seagrass habitats, Sephton said.

Fellow biologist Benedikte Vercaemer said these species turn up in Halifax because of foreign vessels coming into the harbour and Bedford Basin. They usually hitch rides on slow-moving barges or in a ship’s bilge water.

The fisheries department recommends removing the species from boats or draining water once you’re on land, checking the hull before you travel to a different spot, and let diving gear dry out completely.

People are asked to call the N.S. Fisheries and Oceans office at 1-888-435-4040 if they find an invasive species.

Organizations: Bedford Institute of Oceanography

Geographic location: Nova Scotia, Halifax, Korea Bedford Basin

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