Hi guys.
I built my own version of a floating trap a lot like this one -
http://www.texastastes.com/p239.htm I wish I had made the basket deeper like the site's version since I've only caught small turtles so far, but it works. I'll catch 8-10 at a time. The bigger boys can crawl out, so make it deeper. I used white sewer piping about 4" in diam. 4 ft long. Used elbows to make a square frame like the picture. The basket and ramps are hardware cloth. Whole thing cost about $20. This keeps 'em alive and I can transport them to a big nearby public lake. If you have an afternoon to blow and like building things, the homemade version is great. For $99, tho, the commercial version might be a good deal.
It helps to throw some old meat or dead fish in the basket as an attractant.
Good luck with the monster. Here's a good site on snappers.
http://www.chelydra.org/st02.html - mean looking critters!
Happy hunting
Dave
