I would in a heartbeat and would not be made feel guilty for it by anyone.
as you say, these fish are stocked landlocked freshwater fish and cannot breed. Therefore the argument that you killed a 'big breeder' is nothing short of a furphy.
Coupled with the fact that the fish are stocked for the purpose of being caught and taken.
If you want to do it, do it and don't let anyone tell you otherwise. The fish are put there for people to catch and take home, just ask the organisation that does the work.
I'd do it myself cept for the swamp donkey colour, give me a nice metre long chrome salty instead