I'll bet cormorants are doing a job on them, too.. I know for a fact they will DECIMATE trout population. Last year, we had 3 cormorants on our club pond. I fished for 30 minutes in the am one time, and in that time, I saw 2 cormorant take a trout each. IF they aren't eating them, they're certainly pecking them enough to die, later. They are taking over lakes, now, too..