Louisiana is the source of more than 90% of the crawfish consumed in the United States. The state's warm, shallow freshwater ponds -- many of them converted rice fields -- produce billions of crawfish annually, and the industry is deeply woven into the cultural fabric of South Louisiana.
Peak crawfish season runs from March through May. In warm years it can start as early as late January. By June the water temperature rises, crawfish quality drops, and supply dwindles. The best quality crawfish -- firm, full tails, no off smell -- is found from mid-March through April.
Live vs. Frozen Tails
For a crawfish boil, you need live crawfish. They should be active when you buy them. Any that are limp or already dead should be discarded before cooking. For etouffee, bisque, and pasta dishes, frozen Louisiana crawfish tails are an excellent and convenient alternative. Look specifically for "Louisiana crawfish tails" on the label -- Chinese-farmed crawfish, which are often labeled simply as "crawfish tails," have a different flavor profile and texture that does not work as well in Cajun cooking.
Where to Buy
If you are not in Louisiana, the best sources for authentic Louisiana crawfish tails are specialty seafood markets and online retailers that ship directly from Louisiana farms. Several companies offer overnight shipping during peak season. Prices vary significantly by season -- mid-season peak-quality tails cost more but are worth it.