I catch such crayfishes at night. Fresh turrets are knocked over. A little bit later I walk about looking for crayfish approaching tops of burrows. You must be quite or they will retreat back down which can be multiple feet to the water table. When crayfish has been selected as a good target, you then push a shovel blade into soil part way. Objective is have so you can stomp shovel balance of way in behind crayfish blocking it's retreat. The you dig a little with a trowel or simply lever soil out with shovel. Some crayfish will be damaged. Another method requiring more preparation involves trickling water into burrow using a small siphon pulling water from a bucket to simulate a rain. Fishing them out is better for kids to do.