Hi-
Technically it is illegal to sell any wildlife via the Federal Lacey Act. However there are licenses and permits that are "possible" to get. This federal law says no, you cannot sell or transport live wildlife. If a fish farm that is licensed sells catfish, trout or Largemouth Bass etc, yes that is ok. That wildlife has been in captivity and are offspring of essentially fish that are legally privately kept. Where the law is clear is wildlife taken from the wild cannot be sold. According to the law, no ifs, ands or buts. ( Minnow dealers have a special set of regs and permits in each state. )
So what is the answer? Can you sell wild gars? The answer is that wild caught, even with the proper over the counter fishing license, you cannot sell wildlife even if legally taken. That is a bummer for the collectors.
Transport is illegal in many states and across state lines. There may not be enforcement of the Federal law however. I think the spirit of the law is to prevent commerce of wild caught wildlife. I do not think it is actively enforced for "personal or private aquaria" if you catch them yourself and they meet fishing regs.
State laws sometimes allow exemptions for some species to be kept privately, such as "up to four bull snakes" or "six fence lizards" etc.. I have not seen any exemptions for fish, except in WI before the VHS fish disease you could have some wild fish in an aquarium.
It has amazed me to see so many people posting on boards that they have a wild fish to sell. In all cases, without a permit of some form from a specific state, it is illegal. If someone has such a permit from a specific state, for specific species that are caught wild and can be sold, I would like to learn more.
Being a fish enthusiast like everyone here, it is a bummer. One last thing. Those noodling shows where they transport live catfish, many miles and sometimes across state lines is illegal unless the state(s) special permit it. They are violating the Lacey Act. I am glad that they do not enforce it though.
simeon