Koi can live over 40 years and are admired, possibly revered by the people here. You see koi in many water ways including the wild gray variety seen in ditches such as on the walk from the train in Tokyo. These koi can be eaten and we have eaten them, but they are not usually a sport for fishermen. Second class koi such as the photos can be seen in places such as castle (jo) moats. After a few generations they lose their colour and develop the wild dark gray colour. Breeders use tiny tubes to select dark coloured mosquito larvae sized fish from a batch of hatchlings to see whether they will become champion koi. The rest are used as food for other creatures, including rejects at later stages. Fish fertilizer is very common especially on the Gando farm, but this is probably made from rejects of commercial fishermen or fish byproducts.