Hey Bukster....I started the "pissing contest". Sorry about that.
Believe it or not, it's against the law (and very bad for native fish) to release any fish you've had in captive care. While you have the fish in your care, you might not even know it but you can spread disease. Think about how many tropical diseases the shiners you purchased came in contact at the pet shop. They usually have a central filtration system which means that basically all of the fish are in the same water.
This country is currently dealing with a very terrible virus that was due to water release in the great lakes. thousands and thousands of fish can die in a single outbreak. It's called viral hemorrhagic septicemia (OR VHS).
Basically it's important to never release any fish anyplace once you have taken it home. It's also against the law. The rule is.....once you take it home it's yours for life. If you make a mistake and the fish is too big for your tank, it's much better to kill the fish rather than release it.
Sorry for the lecture but this is a very real problem that we must take seriously.