Larry,
I live in eastern Manatee County. My pond is about 4 years old now. Walking catfish are spreading throughout S. Florida brought here from Asia either through accident or purpose. As to what they mean to you, they are like weeds in your garden. No matter what you do they will always be there. The biggest problem with them is that they are prolific, consume fish pellets, and don't get very big. However, I have caught a few 12-16 inch ones which are just as tasty as their American cousins. Just kill everyone you catch.
Toby