I built a 3 or 4 thousand gallon pond in 2004 with a waterfall pump submersed in the nearby trout stream bringing fresh water in, and the overflow goes back to the river in a 4" drain pipe. Its about a 10' rise from the creek. I stocked it with 3 or 4 small koi from a local nursery, but later I inherited a dozen or so koi, about 2007, all big fish more than 12" in length.
About 3 years ago, I saw a hawk on the riverbank picking at a large fish carcass. I went down and discovered it was one of my large koi, about 14-15" in length. I checked my pond and discovered I had about 3 missing. I covered the pond with "bird" netting, and thought the problem solved. About 10 days later, I discovered I had only one large koi left in the pond. No way was it a bird that raided my pond. We do have an occasional otter, sometimes pairs of otters, go up and down the stream. I suspect that is the culprit. I waited a year or two before adding a new pair of adult koi, which are now breeding, and no sign yet of any otter. Not sure if there is a way to keep otter out, they can push right under the netting.
I've also seen blue heron on the edge of my pond, and some of the fish had scales missing where the heron had apparently tried to catch them unsuccessfully.
About 3 years ago, I saw a hawk on the riverbank picking at a large fish carcass. I went down and discovered it was one of my large koi, about 14-15" in length. I checked my pond and discovered I had about 3 missing. I covered the pond with "bird" netting, and thought the problem solved. About 10 days later, I discovered I had only one large koi left in the pond. No way was it a bird that raided my pond. We do have an occasional otter, sometimes pairs of otters, go up and down the stream. I suspect that is the culprit. I waited a year or two before adding a new pair of adult koi, which are now breeding, and no sign yet of any otter. Not sure if there is a way to keep otter out, they can push right under the netting.
I've also seen blue heron on the edge of my pond, and some of the fish had scales missing where the heron had apparently tried to catch them unsuccessfully.
