Although crayfish are abundant in American streams and lakes, until recently, they were marketed only in Louisiana and a few outposts on the West Coast. Today crayfish are beginning to work their way into the culinary mainstream and are appearing in fancy food markets around the country.
To make good soup, you need live crayfish. They’re useless if they’re dead, because there is no way of telling if they died five minutes or a week ago. You can also buy packages of crayfish tails if you want extra tails for garnish, but to prepare a flavorful broth you’ll need whole crayfish, shells and all.