In May 25 1966, Dr. Komei Koshihara made a broadcast to the whole Japanese nation through Nippon Hoso Kyokai Radio Station about the story of koi Hanako. At this time, Hanako was 215 years old weighing 7.5 kilograms and 70 centimeters long. He explained that the koi was passed down from his grandmother on his maternal side, who had inherited the fish from “olden times.” Dr. Koshihara described Hanako as his dearest friend.

While nobody knows the exact reason for her amazingly long lifespan, perhaps the crystal clear waters of the Japanese mountains and the great love and care of her owners was the key.

Koi Lifespan

Koi fish are known to have a long lifespan. However, their lifespan can vary widely depending on the fish's environment and genetics. In the wild, life expectancy of the common carp is approximately 30 - 40 years. In captivity, the average koi lifespan is 70 years. In fact, it is quite common to witness a koi that is over a century old in Japan. This is one of the reasons why koi fish have gained so much admiration in Japan and the rest of the world as well.

Environmental factors that contribute to a long lifespan are clean water, quality koi food, and long cold winters. The cold season will slow down the koi’s metabolism drastically. During this period, the fish may eat very little. In fact, during the coldest winter months, it is recommended to completely stop feeding as described in the Koi Feeding Guide.

Genetic factors also play a significant role in a koi’s potential lifespan. In Japan, these ornamental carp are called Nishikigoi. They are bred for specific traits such as their body shape and coloration. Of course, large size is a desirable trait, but only if the body shape and coloration is maintained. Outside of Japan, koi are often bred for different characteristics. For example, the popular butterfly koi are bred to be much hardier and exhibit faster growth. Therefore, a koi fish that live over 200 years like Hanako, is extremely rare.

Next to whales, turtoises, and tuataras, koi fish are one of the longest living vertebrae on Earth. Koi Hanako is a great example of how long koi fish can actually live. In fact, she is the longest living freshwater fish ever recorded.