you would have to put them in the checked bags. Only allowed to have small volumn of liguid as carry on. I have packed someting similar in my checked baggage with no issues several times before. I am not sure about customs on the way out. I am not even sure they are worried about what leaves as long as its not drugs. Countries seem to be more worried about what comes in.
They might not even know what kind of fish they are, if that matters.
If they will let you bring in 10 fish, it should work as long as customs lets you leave with them. Keep your receipt from the fish farm just in case. But most likley they will not know any thing differant then they are little fish.
Customs officers are not DNR or Fish and Wild life officers.
