Dont know if your allowed this there but these 2 types of crayfish traps are very sucessfull around my part of the world.1 shot said:
Rig 1 ( Normally used from the side ) - Use your pole setup and still have your net handy but instead of a hook, attach a mesh bag to the end of your line, a large hole shading net works best, almost like a pool net, your bag doesnt need to be bigger than say 10x10cm. Fill the bag with bait and squash it a bit so your creating like a chum, we use sardines. Lower the bag and there you go, the crays that get on get stuck in the holes, you simply lift em out.
Rig 2 ( Used from boats ) - Take a bicycle rim without the spokes and line it with rope net, to make a basket effect if you lift it, holes the size of the trap shown on the page should work fine and add a rope or float line tied to 3 or 4 places on the rim so it hangs straight when you lift it, if using more than one tie a float to each line as marker. Attach your bait bag to the centre and lower it down check on it every so often and remove the catch stuck to the net.