Hi Stephen, I would agree, a heron could land there easily and I bet thats whats had your fish. I often see people advised to 'give fish plenty of cover' to protect from herons but quite honestly, thats a waste of time. As an angler, I've watched herons fish on countless occasions and they stand like statues motionless until the fish swim past, then, as quick as lightening they strike and rarely miss ! Ive watched them take small eels as well and if you have ever handled (or tried to handle) eels, you'll know just how hard they are to grip but the heron has no trouble ? They are very patient hunters and once they find a pond, will return again and again until they have cleaned it out !
Lannerman.