The other day when I was fishing, I saw a Mink come down, swim and catch a Trout! I thought that they could have Feeding Zones where they chase fish or at least look like they're eating a fish, they would have similar mechanics to Beavers and Alligators, where they could swim away.
They would go up to either Level 3, or Level 9.
I think they would be another fun animal! And could be added maps with rivers or small ponds.