In 1765, after refusing to swear allegiance to the British Crown, the French Catholic settlers of New Acadia (Nova Scotia) were exiled by the British. More than 10,000 Acadians resettled in the bayous of southwestern Louisiana. There they discovered the red swamp crayfish, sweet reminder of the lobsters of the north and of the écrevisse , the native crayfish of France, as Cajun folktales and recipes reveal. They spun a tale of how the crayfish came to Louisiana: The lobsters were huge up in Acadia, as big as a man. Only one chose to follow the Cajuns into exile. During the long and difficult trip, it grew smaller and smaller. By the time the exiles reached Louisiana, the lobster was only a few inches long.
Soon the Cajuns were farming Louisiana crayfish in their rice fields, using an ancient practice developed by the Chinese. Procambarus clarkii seems particularly suited to cultivation––able to colonize disturbed habitats unsuitable for the native crayfish––and this led, in the 20th century, to its introduction across the US and around the world. P. clarkii is marketed by biological supply companies for teaching and research. It exhibits different color morphs, including white, blue, and orange, which are sold in pet stores in Europe. It has been introduced for aquaculture in Arizona, California, Georgia, Hawaii, Idaho, Indiana, Maryland, North Carolina, Nevada, Ohio, Oregon, South Carolina, Utah and Virginia. In Washington it appeared after it was sold as fish bait. (Crayfish easily fall off of the hook, so casting should be slow. Unused live bait should never be dumped into a body of water. Or on the shore: individuals are reported to be able to cross many miles of relatively dry ground, especially in wet seasons.)
The species has also been introduced for aquaculture to Central and South America; Europe (Spain); East Asia (China; Japan, as a food source for bullfrogs––another American import––now crayfish are common family pets); and Africa (Kenya; Egypt; Nigeria––because it prefers many aquatic and semi-aquatic snails that are vectors for human pathogens such as schistosomiasis). A recent paper in PLoS ONE noted that crayfish may be moving out of ponds in the footprints of hippos, where perhaps they’re being harvested.
The result of all this interchange? The ultimate irony: Louisiana crawfish production has decreased in recent years due to increased imports of red swamp crayfish from China so cheap they undercut the native ones. China, where rice-fish companion farming originated long ago, is now the world’s leading producer of North American red swamp crayfish.
