Yup, they're dead. In
very large numbers.
They die in aquariums, in 80 gallon koi ponds, in water features, in "natural" AS ponds and AWGS rock-bottomed, slope sided, plant-infested puddles.
With luck, the koi aren't killed straight off by their owners and get to grow until accumulated waste and pathogens overwhelm them. Within a year or two the wheels have fallen off and the koi are dead. All across the world. Every year.
So they buy more koi. Repeat endlessly. Don