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Blue Crawfish Baffles Aquaculture Professor

US - Researchers at the Northwestern State University Aquaculture Research Center are studying a strange crustaceous phenomenon: crawfish that turn permanently blue.

“We are thinking of calling them ‘Cajun Blues,’” said Dr. Julie Delabbio, professor and director of the Center, located south of Natchitoches on the Red River near Lena. “Or maybe ‘fleur de lis’ crawfish because the blue color is really close to the royal blue color of the French king.”

NSU staff and students began a research project last summer placing ordinary brown-red Louisiana crawfish in aquaria at the Aquaculture Center. Four months later, more than 60 percent of the crawfish are vivid blue.

“Our research was not aimed at changing the color of the crawfish. We were investigating whether lengthening the amount of light that crawfish receive each day would make them grow larger or faster. The color change was a complete surprise,” Delabbio said. “There are some species of crawfish which are naturally blue, and on a rare occasion you will find a blue crawfish in a crawfish pond. But 60 percent of the ordinary-colored crawfish in our research study turned blue and continue to stay blue even after they molt.”

Other scientists have offered various suggestions as to why the dramatic change in color has occurred. Explanations could include diet, the light spectrum, or, since the crawfish are housed in a blue tank, a means of camouflage.

“We know that it is not genetic,” Delabbio said. “Is the color change permanent? We don’t know. But blue crawfish sell for $25 a piece in the aquarium trade.”