The Case of the Missing Koi

To tell my story properly, I'll start from the beginning. We bought our house about 5 years ago. Neighbors tell us that there were huge ponds in our back yard at one time, possibly created by the first owner of the house? They say that when that owner moved, a tanker truck came to load up all the fish. At some point someone (wisely?) decided there was too much pond to manage and it was filled in. However, one small section remained unfilled. We bought this house from a young couple that had several small children. The "pond" was in a sorry state. It was filled with leaves, did not have any kind of filtration system and an old pump was sitting in the bottom covered in leaves. We thought it would be neat to clean it up and get it back in order. Later we learned that in order to have koi, we would need it to be deeper, at least 24" for them to survive the winter. So we paid to have the pond redug and all new rocks put around. And I thought it would be cool to have a bench made of stone to gaze upon our fish.
We bought some koi 2-3 years ago in the spring. They were nicely sized when we bought them and it didn't take long before they were huge, probably about 15" long. We filled in the pond with some goldfish too and had about 13 fish at one time. We did notice some breeding going on and knowing that the fish would eat their eggs, I rescued the eggs, put them in a bucket and they started to wiggle and hatch. At one point I added something to the water (can't recall what) and I killed all life in the bucket. I was devastated. But we still had the 13 fish, so all was well.
During the winter, you stop feeding the fish and they go "dormant." They hang out at the bottom and don't really swim around. When the temperature warms up and the water gets warmer in the spring, they start swimming again and you gradually feed them. Well imagine our surprise when we notice during the winter 2 years ago that all the fish have disappeared. Every one of them. We were perplexed. If they had died, it would seem that they would be floating around or there would be some evidence left. No, all gone, not a clue left. We thought maybe a hawk, heron or crane could have swooped in and eaten all of them.

So this spring, we decide to try again. This time we buy three tiny koi (about 6"). We don't purchase any goldfish. They do great during the summer. They go dormant in the fall/winter. Then poof, they are gone again. No trace.

I have researched all the possibilities and there are so many critters that could have eaten the fish. However, we talked to an expert and he feels certain that it's a raccoon. And John did spot a raccoon in the subdivision a couple months ago. It's really difficult to cover the pond with an animal proof net. We are thinking of getting a night vision camera like hunters use to see what's going on and we have a large trap. But we're told it's too late to try to trap a raccoon, so I guess we'll have to wait until next year. I have mixed feelings about having a pond without fish. It's just not the same. I suggested to my husband that we fill it in and expand the deck or build a fire pit in that space. But really, I would to be able to watch the fish again! It's such a relaxing way to spend a summer evening.