Awww... that's so terrible. It's my worse fear.

Sound like a Blue Heron has been using your pond as a buffet. I had the same thing happen to me about two years ago. Once morning, at about 6:00 am, I was sitting on a a bench next to our pond, thinking this over, when a Blue Heron came in for a landing and damned near hit me!!! Three hours later, i was at my local pond shop talking to the owner about this. He said the best thing to do is two-fold. 1) Buy a plastic Blue Heron (http://www.nextag.com/blue-heron-decoy/stores-html) and place it near your pond. Blue Heron's are territorial so when the real one sees the fake, it will normally leave. Thing is, you have to move it just about every day. 2.) Buy a motion activated Scarecrow water sprinkler (http://www.safepetproducts.com/scarecrow-motion-sprinkler.html). In your case, since you have so many predators, I recommend the water sprinkler.

I went with the water sprinkler and this baby works great! In the past two years, I've seen that Blue Heron get sprayed half a dozen times each summer. Wonderful to see that thing get scared and take off. After a while, it stopped coming around but I have seem it again this year and the same thing happened. Ever since I got the sprinkler, I haven;t lost a single Koi but this year, just for GP, I bought the decoy heron too.

Good luck!

Alvin

Raccoons will kill multiple fish without eating them or taking them away. They often bite off their heads or if too big bite at them and move on.