Check the source of any frozen crawfish you find in the seafood market or grocer’s freezer section. If possible, avoid using crawfish from China. My experience is that the “fat” in the imported tails is bitter and needs to be rinsed off the tails before you use them. The likely reason for this is the extended time it takes for the imported crawfish to reach the market. Crawfish fat will go rancid after a couple of months, so if you do use imported crawfish, make sure to rinse the fat off thoroughly. Not optimal, but it’s better than bitter-tasting crawfish.