Researchers try to outpace invasive slimy sea squirts

Scientists are racing to outsmart the next invasion of sea squirts, a species that ischoking the mussel industry in Nova Scotia, before it can even start attacking shellfish farms.

Dalhousie Universityprofessor Sarah Stewart-Clark wants the public to know an invasion is underway in Nova Scotia.

"Be on the lookout for species that aren't supposed to be in Nova Scotia but have arrived here," she said.

Invasive tunicates also known as sea squirts are slimy creatures that attach themselves to mussels and either rob the shellfish of nutrients and water, or literally rip the mussels off the rope they attach themselves to with their sheer weight. They are invertebrates that look like giant orange slugs.

Stewart-Clark said several species of tunicates only recently starting growing out of control.

"We have warming water temperatures that are really playing a role," she said.

"Species where our cold water used to inhibit their growth and survival, having a few degrees warmer in a bay will allow those species to grow a lot better."

Just one tunicate can produce 10,000 more.

Some mussel farmers in Nova Scotia on the South Shore of Nova Scotia say their businesses are being destroyed by tunicates.

"We've probably lost about 50 per cent of the industry at this point," said Bruce Hancock, with the Aquaculture Association of Nova Scotia. "The only operations still continuing are ones that dont have tunicates."

Researchers said for now, there's not much they can do to get rid of the invasive species that are already here. Instead, they're focusing on detecting and eliminating any new species before they have a chance to spread.

Stewart-Clark said they can now detect tunicates' DNA at the egg and larval stage.

"The hope is when the next invasion comes we'll detect it right away and be able to isolate it to that bay," she said.

Still, those in the mussel industry say something also needs to be done to help farms already infested with tunicates.

"If we don't put proper supports in place to keep these farmers here and we can't get to the bottom of how to grow mussels economically under the conditions such as having tunicates, then we will lose the industry," said Hancock.