I thought it a good idea to revive this thread with a new bit of info.

BG nest site selection article in the new In-Fisherman issue by SDSU student Quinton Phelps and our own Professor Dave Willis.

In this lake every BG nest site had a substrata of small gravel despite the availability of sand , rock and muck at other locations. No other habitat characteristic seemed to be a critical factor that influenced in nest location. It is good to know that this forum was on top of this 14 mths prior to In-Fisherman. Cutting edge !! - right . \:D

There is also an article on crawfish life cycles.