The World's Oldest Fish (a Koi!)
If well cared for, your koi could live for as long as 50 years. Some will live even longer lives and their age can be determined by counting their annuli, which are growth rings on their scales. A celebrated koi named Hanoko was estimated to have reached the age of 226. Either Hanoko was the world's oldest recorded fish or the scientists who examined her made a huge miscalculation!
Hanoko spent her life in a pond of crystal clear water at the base of Mount Ontake in Gifu, Japan. Her name means 'Flower Maid' and she was a beautiful scarlet koi. She had outlived several owners in the same family when her last keeper, Dr. Komei Koshihara decided to have her examined in order to determine her age.
Hanoko's age could be estimated via a microscopic examination of her growth rings which were too small to be seen with the human eye. Two scales from different areas of her body were carefully removed for testing, which took place at the Laboratory of Animal Science, Nagoya Women’s College.
The tests were overseen by Professor Masayoshi. It took two months to achieve a reliable result from the examination which revealed that Honoko was probably hatched in 1751! This was 25 years before American independence! The fish had lived through the French Revolution, the Battle of Waterloo, the abolition of slavery, both World Wars and man's first steps on the Moon.
The aging of fish is not an exact science but is known to be reasonably accurate. The estimate of Hanoko's age was supported by the anecdotal evidence of the Koshihara family.
Hanoko lived her entire life in the same pond. She was a friendly fish who would come to the pond's edge to be petted and could be hand-fed. She died 7 July 1977 and weighed 7.5kg. The reasons for her incredible longevity are unclear. She was obviously cared for well by her successive owners but it was almost certainly her genetics which dictated her lifespan.
Something in the Water?
Hanoko shared her pond with five other fish. These were also tested over the course of a year to establish their ages and all were found to be over 100 years old. Perhaps there was something in that Japanese water after all?
If you keep koi then perhaps one of your fish could reach a heroic age. It is entirely possible that your fish could outlive you so it is wise to make plans for their care in the event of your death. You are able to make financial provision for your koi in your will and to specify how they should be cared for. This could give a koi lover a greater peace of mind.