I used to catch them all the time by the lake by my house when I was younger. This isnt by any means a solution, specially if you have alot of them, but just trying to help. There would usually be two of us, one would actually go up to the hole and actually pump your fist through it and with the pressure the crayfish would fly out of another hole and thats how we caught them, obviously if you have hundreds it could take awhile.......wish you luck.