Something you might consider doing is volunteering to go out with some of the DNR fisheries biologist when they are doing stream surveys. While they aren't the ones who know what the policies are regarding selling fish, you will get some great references that could help open doors that might normally be closed. You will also get knowledge of and access to sites that would normally not be accessable. Also you get better at your fish ID skills.
Doing this helped get us a lot of contacts here in our state. We also provide collection data (locations, species & quantities found) to the DNR whenever we go out. Have found several populations of Elassoma that were previous not known to be in certain areas as well as a species of killifish not previous recorded in SC. Also have possibly found two new species of mudpuppies (Necturus) pending DNA testing.
Chip in SC