Keeping tabs on invasive shrimp in local waters
Old Saybrook — On just her third sweep with the long-handled dip net, Ellie Bors found what she was looking for.
"Guys," called Bors, a doctoral candidate at the Woods Hole Oceanographic Institution, to the four marine sciences interns working with her at the Town Dock. "There's huge ... lots of shrimp here. And you know what's interesting? I got all these from the sediment."
She emptied the net into a shallow metal bin, examining each of the translucent, antennaed shrimp, the smallest about the size of a teardrop, before placing them into a sealed container for lab analysis.
"Sometimes it's really hard to tell what kind of shrimp they are until you get them under a microscope," said Bors. "On some level, shrimp just look like shrimp."
Bors and the four interns, part of the Williams College maritime studies program at Mystic Seaport, sampled three sites on the Connecticut River in Old Saybrook Friday as part of an East Coast survey this summer for three types of invasive shrimp, two from Europe and one from Asia. They were also looking for a fourth type native to Florida that was found last year at Woods Hole, far north of its normal range. The purpose of the surveys is to determine the distribution and abundance of these shrimp, and at the same time assess how populations of native grass shrimp are faring.
"It's a matter of whether the invasive shrimp will disrupt the role the grass shrimp play," said Nancy Balcom, associate director and extension leader at Connecticut Sea Grant, which is helping fund the surveys along with other Sea Grant branches from Maine to New Jersey and the state of Massachusetts. Connecticut Sea Grant is based at the University of Connecticut's Avery Point campus in Groton.
There are multiple efforts to try to prevent invasive species from entering estuaries such as Long Island Sound, including controls on where ballast water from shipping vessels can be discharged, Balcom said. Once a species enters an ecosystem, there is little that can be done to stop its spread, other than to keep tabs on how it's affecting other marine life, she said.
The European and Asian species, first found on the East Coast in 2001, are important parts of fish diets in their native ecosystems. Locally, the invasive shrimp project is being led by James Carlton, professor of Marine Sciences and director of the Mystic Seaport-Williams College program. Each week since June, the four interns have been sampling the Mystic River near the Seaport, at high and low tide and various times of day, to establish baseline data on the invasive shrimp and any changes in their abundance.
Since June, the group has collected one set of samples at brackish waters throughout the Northeast, finding them in some places they expected and others they didn't, Bors said, and are now working on their second set. Before coming to Old Saybrook, the group had been to Maine, New Hampshire, Cape Cod and Rhode Island, and were heading next to three sites in Milford before traveling to New York and New Jersey next week.
"It's not uncommon for invasive species to be in estuaries, because they have higher tolerances" for differences in salinity, Bors said. "And also a lot of ports are in estuaries."
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