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A live red swamp crawfish. Residents of Old Greenwich, Conn., have found crawfish shells on the shores of Long Island Sound.

(David Grunfeld, NOLA.com | The Times-Picayune archives)

Residents of Old Greenwich, Conn., are scratching their heads over the discovery of crawfish shells along their Long Island Sound shoreline, according to the Greenwich Time.

Residents found a half-dozen molted shells around one dock in Old Greenwich and another shell in Riverside recently, and at first thought they were juvenile lobsters until a high school biology teacher gave the creatures a proper identification, though using the northern term crayfish.

Based on a photo of the shell accompanying the article, the crawfish they found would be known in Louisiana as the red swamp crawfish, which has the scientific name of Procambarus clarkii, according to Robert Romaire, an aquaculture specialist with the LSU AgCenter. He said the paper's photo did look like the shell left behind when a crawfish molts and grows a new shell.

"RS crawfish can pretty much be found in many northern states nowadays, but not in significant abundance (with a few exceptions)," Romaire said in an email response to a question about the article. "We get inquiries and RS crawfish photos from other states from time to time, including Alaska, Wisconsin, etc., and northern Europe (Sweden, Netherlands, etc.) and maybe a few other northern states where RS crawfish show up from time to time."

The newspaper pointed out that crustaceans have been scarce in the western end of Long Island Sound since a die-off of lobsters took place in 1999, which has been linked to pesticides, algae, warmer water and low oxygen water conditions.

Crawfish generally live in fresh water, however.

Romaire said there are a variety of ways the non-native species could have traveled to Connecticut, including being shipped from Louisiana for a crawfish boil: "Cajun is everywhere," he said.

But that species of crawfish often are shipped to schools and universities for use in biology laboratories for research and to aquarium hobbyists.

"Often when laboratory studies are completed or a hobbyist tires of the animals, the crawfish are released because people don't have the heart to kill them when disposing of them," he said. "Adults should know better, but younger kids don't know of the potential ecological consequences."

Several European and African countries have reported problems with non-native crawfish species outcompeting native species, and threatening their survival.