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I think they do, mostly based on breeding. But these are variables in any genetic pool. So we talk about averages and that is a combination of genetics and environment ( environmental stresses).
So in the 1970s and 1980s most koi ony lived to 3 or 4 with most dying in their first year or two of life. Improvements in technology, pond design and diet, soon changed all that and had some living easily to 10-12.
And those stats have increased steadily up to today. Today, koi seem to die of natural causes as much as , if not more often than, disease and environmental crashes. In truth, most koi are still slowly worn down by closed systems and this is still a factor, albeit more subtle.
I would say that as a generalization, gosanke live 18- 23 years typically. And some varieties have 'been known' to live to 28- 35 years of age.
And some wild carp have been documented to be 50 years of age in captivity. Yet the studies done of prototype wild carp in the Caspian and Black sea regions find that the bulk of the population ( greatest numbers) is in the age group of 3-5 and that numbers decline from there, with 14 being an 'old fish'. This however might have to do with fishing and predation.
Against that data you can add:
Too many koi still only live to be less than two years of age.
There is no such thing as a 150 year old koi.
JR
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