I agree you should ask if a person who finds an invasive goldfish could keep it as a pet. Afterall, it is not dangerous and doesnt require a license or a person with specialized training and qualifications (like a wildlife rehabilator) to keep. If they say a person who catches the fish cannot keep it, ask if they would be willing to let the fish live if you relinquished it to a local shelter or rescue group. Of course that means you'd have to get in contact with some local organizations to make sure one would be willing to take in a fish. A rescue group for reptiles &/or exotics might take it, or maybe even a "regular" cat/dog shelter. In fact, petfinder.com even has a "scales, fins, and other" section where if you look, there are groups that sometimes have fish needing new homes.
While I can understand why they want to have the fish I can also understand your frustration as it would be a shame after all your hard work to catch it and all its hard work to stay alive it had to be killed. It makes sense to remove and euthanize members of an invasive species when there are multiple individuals which for a multitude of possible reasons can't be kept alive in captivity, for instance when there not enough appropriate knolwedgeable places willing to take the animal, the animal gets too big, is too dangerous etc, however in this case it does seem a bit unfair for one fish to be killed. Especially when the fish is possibly just a "one off" individual released by an irresponsible owner who no longer wants it. One fish which is not dangerous, which has already been removed from the native ecosystem, and which can relatively easily be kept by "regular" people without a permit, as opposed to an animal that must go to a zoo, sanctuary, or specially trained/licensed person. However on the other hand, I do of course understand why they not only want the fish removed but want the body as well, and I suppose they can't make lots of exceptions.
Like others said, you could just report a sighting, as opposed to telling them you have the captured fish. I'm not sure how it works, but if someone reports a sighting of an invasive animal, they might send someone out to look for the animal and to make sure there isn't an established, possibly breeding local population. And if there is no established population and you have already removed the animal reported in the sighting, it's making them go out there for nothing. But like someone else said, you could say the fish died. I'd say keep researching your local laws to make sure you're not doing anything illegal. I think it's fantastic you even cared enough to go to all the trouble to catch the fish, lots of people wouldn't have done that! Keep us posted.
Last edited by JustinieBeanie; 09-15-2013 at 11:45 PM.