BC,
Some possibilities include 1) poaching by birds (aka water turkeys, herons, etc,) 2) poaching by animals e.g. otters and of course 3) poaching by humans. I've experienced all three and they have made a tremendous negative impact on my bass population. The human poaching not only resulted in removal of fish, but it also caused the bass to become "educated" to where they will only very rarely take artificials and will only feed on live bait, i.e. small blue gill. I now have all three problems under control and am in recovery. Perhaps you have experienced some of these also.
