Invasive sea squirts found in Cobscook Bay

EASTPORT – Scientists and naturalists are planning to monitor Cobscook Bay after the discovery of an invasive species that could prove dangerous to the local scallop- and urchin-fishing industries.

A team of researchers found the marine animal, a species of sea squirt called Didemnum, in less than 20 feet of water in the bay off the coast of Eastport two weeks ago.

Until now, the Damariscotta River was the northernmost point along the Maine coast where the species had been identified.

A type of tunicate that grows in colonies and clings to hard surfaces such as rocks or pilings, Didemnum can spread rapidly along the ocean floor, in an outward rather than upward direction.

It also has been found in Casco Bay, as well as Long Island Sound in New York and Georges Bank, where it has expanded from a 6-mile coverage area to 40 miles in the span of about one year.

According to information from the U.S. Geological Survey, it can harm aquaculture and fishing grounds by growing over scallops, mussels and oysters.

“It’s like a weed,” said James Carlton, director of the maritime studies program at Williams College in Massachusetts and Mystic Seaport in Connecticut. “It grows in these great … gelatinous masses. It is sobering to find it all the way up near the Canadian border.”

Scientists are unsure what effect the tunicate will have on the local fishing industry, a critical component of the regional economy. Scallop and urchin landings in the area represent about $3 million annually.

“It is definitely a concern that this stuff is present,” said Will Hopkins, executive director of the Cobscook Bay Resource Center in Eastport. “It is something that needs to be monitored. There is definitely some value at risk here.”

Local fisherman Bruce McGinnis first noticed the sea squirt species about two years ago in one of his fishing nets, Hopkins said. A tentative identification was made after McGinnis, who has since passed away, described its consistency resembling pancake batter to University of New Hampshire professor Larry Harris.

When a group of about 20 marine biologists traveled to Eastport earlier this month to look for the presence of invasive species, they included the area where McGinnis made his observation.

So far, no other fishermen have reported finding Didemnum in the area, Hopkins said.

Marine scientist Robin Hadlock Seeley of Cornell University in New York said the next step is to determine whether the species is located elsewhere in the bay and whether it is spreading.

“We have no idea how widespread it is,” said Seeley, who helped organize the invasive-species search in Cobscook Bay. “Nobody is pushing the panic button right now. This is not a crisis, but it is something to watch.”

Overall, the findings of the invasive-species search were good. The bay has very few non-native organisms, especially when compared to Casco Bay and other parts of southern New England. That could be because of the frigid bay water, Seeley said, adding that the cold also may be preventing the proliferation of tunicate.