I am aware of the St John's River population. But those aren't offered for sale, and even if they were, the common FW captive set ups can't deal with the ammont of waste they are producing to live in FW. The ones we see pop up are really marine animals dripped over to FW. Typical captive FW environments cannot properly offset the increased waste production like they have adapted. They produce roughly 10 times more waste in freshwater. So if you keep one in a 400 galon marine tank, that would translate to a 4,000 gallon freshwater tank. People need to be aware of that instead off falling for poor sales tactics.