Invasive sea squirt discovered in Cobscook Bay

Researchers have found a marine invasive species in Cobscook Bay that has coated areas of Georges Bank, threatening to interfere with fishing. However, scientists are hopeful that the waters of the bay are too cold for the species to cause much impact here.

Larry Harris, a professor at the Center for Marine Biology at the University of New Hampshire, found the tunicate Didemnum, or sea squirt, in the area of the old toll bridge between Eastport and Perry. Because the tunicate can reattach itself and continue to spread even after it is broken up, draggers provide one possible way for the species to spread.

On Georges Bank, about three years ago a survey found the species had covered about 90% of the bottom in a six-square-mile area. Last year researchers found it covered about 40 square miles. The sea squirt can spread rapidly, altering marine habitats and interfering with fishing, aquaculture and other coastal activities. It covers everything and "may even smother scallops and mussels," says Harris.

"It's probably too cold for it to be a pest in this region," he adds. "Cobscook and Passamaquoddy bays are blessed by being a little too cold for a lot of things for them to become major pests here."

The sea squirt, which is believed to originate in Japan, was first documented on the east coast of the U.S. in the 1970s in the Damariscotta River. According to Harris, government labs had been introducing Japanese oysters into Maine estuaries for aquaculture, with the University of Maine's Darling Marine Center on the Damariscotta involved with aquaculture beginning in the '70s. The Passamaquoddy Tribe tried to establish an oyster farm near the area of the old toll bridge in the late '70s with oysters from the Darling Center. "That was probably how it got here," says Harris.

Harris was among nearly 20 marine biologists from around the country who were in Eastport and Lubec on August 7 through 10 to take part in a Rapid Assessment of Marine Invasive Species in Cobscook Bay. The project aims to assess the size of the marine invasives problem in the region and potential threats. Organizers of the project include The Nature Conservancy, Cornell University, Maine Sea Grant, Cobscook Bay Resource Center and the Maine Department of Marine Resources.

"We've been seeing mostly native species," says Dr. James Carlton, director of the Maritime Studies Program of Williams College and Mystic Seaport. "There's nothing so far like is seen farther south."

Carlton says invasive exotic species are considered "one of the top problems in ocean conservation," causing major impacts worldwide. "No coastline is immune from possible invasions."

The Cobscook Bay survey will form a baseline of what species are in the area now and their relative abundance. Although scientists don't always know if a species is invasive, Carlton says most of the ones that they are concerned about are known to be invasive. And Cobscook Bay has been sampled since the 1840s.

Carlton says there is a great amount of interest in preventing the spread of invasive species, noting in particular their economic impact. In the Gulf of Maine, the European green crab nearly "did in" the soft-shell clam industry over the past 50 years, he notes. And zebra mussels in the Great Lakes will have an estimated $5 billion economic impact over the next 10 years.

Exotic species can be predators of or competitors with native species, or they can be agents of disease. By replacing a native species they can directly or indirectly affect other species harvested by fisheries or aquaculture for seafood products.

Invasive species can be brought into an area through ship ballast water, the hulls of boats, new developments in aquaculture or the bait and live seafood industries. Carlton says the nori farm in Eastport in the 1990s that used a Japanese strain of the seaweed was watched worldwide to see if the seaweed would spread into the bay.

The researchers have been sampling specific types of habitat, such as floats, docks and pontoons. They have found classic older invasive species, such as the European green crab and the European snail or periwinkle, along with newer ones such as sea squirts and bryozoans. Members of the team hope to discover how many marine invasive species are present in eastern Maine and project their potential impacts on the environment and the economy.