Lordy, I hate to tell the world, but CRAWFISH, as they've become known here in south La., are a huge business. Crawfish boils are held at all sorts of events [I've been to a couple of wedding receptions where boiled crawfish were served - - along with the more traditional items]. Messy to peal & eat, but worth it. Just to give you an idea of what's going on, here's one local site:
http://suckdahead.com/
You only eat the tailmeat, like a lobster. But the head & thorax, which are actually the larger part of the beast, pick up quite a bit of the seasoning [usually Zataran's Crab Boil + other stuff] in the water. Most of the locals suck the innerd out. Yeah, I know, it sounds gross, but don't knock it till - - - - & of course there are t-shirts on Bourbon St. about suckin' heads & pinchin' tails that has fun with it. Other goodies, from new potatoes to corn on the cob to sausage, are often boiled along with the mudbugs - - they are delicious too.
Crawfish have been very scarce for the last 3 years or so due to the drought. This has been a slightly better season, but supply is dwindling now & the price is edging upwards.
Sorry to go on, but had to pitch in.
Oh, sorry - - don't have any solution to the mounds they make in your yard. When I've caught my own crawfish, it has been in shallow water, using crawfish nets baited with chicken/turkey necks or better yet, calf spleen, called melt. But I go on . . . . .