RE: Fat On Crawfish ??
Fat on includes the "fat" or digestive "juices???" of the crawfish. It is yellow or pale yellow/green, depending on what the crawfish is eating at that time (season). Very rich and used in lots of Cajun recipes featuring crawfish. We used to be able to buy it in 1/2 pint containers when we bought frozen crawfish, but I haven't seen it lately.
You can do without the fat, however. I love it, but my wife doesn't. If you need to replace the fat with anything try an equal amount of cream of mushroom or chicken soup. Not the same taste at all, but a good substitute.