Hey David I know this was posted awhile ago and hopefully you found a place to catch crawfish. I live just 45 minutes north of Manhattan close to the blue river (same river feeding turtle creek in manhattan) and I have caught tons of crawfish in my minnow traps. Have never set a minnow trap in a large river personally, but have had good luck catching crawfish in the smaller feeder creeks. Shallower water along shore, Backwater or slow moving current in about 2 foot Of water seems to be ideal. I’ve used bread and dog/cat food and personally believe I’ve caught more crawfish while using dog food in my minnow traps. Hope this helps, good luck!

-Alec