Two invasive species in Long Island Sound worry marine biologists

New Haven – Two non-native species found in Long Island Sound are raising concerns about impact on the estuary's ecosystem as well as on commercial and recreational shellfishing in the state.

Two University of New Haven marine biology professors on Wednesday announced their findings on invasive sea squirt, Styela clava, and Asian shrimp. Of the two, the sea squirt, native to marine waters off Korea, is of greater concern because it can smother oysters, clams and mussels, as well as foul vessels, traps and other fishing gear.

Professor Carmela Cuomo and her students have been studying the extent of the range of the sea squirt in collaboration with professor Robert Whitlatch of the University of Connecticut's Avery Point campus in Groton.

It and other varieties of sea squirt, also called tunicates, had previously been found and studied by Whitlatch in waters off Groton, Niantic and other areas of the eastern Sound, but Cuomo's research shows the rapidly reproducing Styela clava is growing on docks, shellfish beds and elsewhere as far east as Bridgeport.

"This is truly a potential threat, if they do what they have done in other parts of the world," said Cuomo, head of the university's marine biology program, during the event, on a dock at the city's waterfront.

In a bucket were samples of the sea squirt, brownish-green pouches about the size of a walnut that grow in clusters. Removing the dense colonies that can cover shellfish beds is a very labor-intensive process, she said.

The Asian shrimp was first found on the U.S. Pacific coast in the 1950s, but not found in Connecticut waters until 2010, when it was spotted in the Mystic River off Mystic Seaport. Since then it has been found widely distributed throughout the Sound, said John Kelly, assistant professor.

The shrimp is slightly larger than the two native grass shrimp species in the Sound. The three species look similar, except that the Asian shrimp has a stripe down its back.

"It's rapidly spreading, and it's well-established," he said. There are many questions about how the Asian shrimp will impact the ecosystem that need further study, he said. Among them: will native fish that prey on native shrimp eat the Asian shrimp? Will the newcomers out-compete the native shrimp for habitat? Will they introduce diseases that native species have no immunity against?

Photos of the sea squirt and the Asian shrimp can be found at: http://www.newhaven.edu/news-events/pressreleases/189793/.

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