Wow, you need to create a resale market for those leeches. Those are prime specimens and look very hardy!!

I've tried to find a way to either keep them in captivity to reproduce or to find a local swamp, marsh, lake, stream that would have them where I could trap them. Striking out on all counts. It must be that only certain places have them and they don't breed well in captivity?

or, in the same vein as your tiger salamander research, maybe ALL places would have them providing you had zero fish! Yours look particularly healthy and happy. I wonder how the big bait wholesalers (say in Wisconsin where a big outfit feeds most of the midwest singlehandedly) keeps enough leeches in stock..