(personal comment, I wish the right to shoot critters which are doing damage could be applied to GBH, why should they get a pass?)
You can get a permit to shoot them from the feds as long as you have exhausted all nonlethal means and you raise fish for a living. It's 100 dollars. Sell some fish and come up with a business name?
I used to buy one but have better things to do with 100 dollars, and don't like to kill creatures that are just doing what they evolved to do. They were here before I put my pond in I and made it an attractive place to feed.
Just my opinion and you know what they say about opinions.