We lost a pond full of catfish and was told otters had cleaned us out . Very few catfish survived . The creek that leads to and from our lake is according to game and fish, is full of otters . I killed several muskrats but did not see an otter till it was to late . Things swim under the surface pushing up a trail of water like a torpedo( not sure this is always the case , only saw one ) . Walk around lake/pond looking for trails (look like beaver slides ) and walk them out to search for bones . fish bones that is . We were told the heavy stocking of mussels provide a food source for them . We had catfish mostly up to two lbs . when we noticed a decline.Will eat you out of house/home in a matter of weeks we were told .