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How are you able to tell what gender the koi is? I have heard from a source that the fin shape gives me a clue what the gender is. Also how could you determine the age of the koi? I thought I want to verify it.

McCollum

Very tricky questions there. Basically because either the age or the sex is hard to confirm without actually opening the fish up, or giving it an x-ray to see whats inside.

The oldest koi authenticated was in japan, it made a humbling 220 years. However this was kept in cold conditions in a natural setting. Most captive koi without having practically a lake of their own will average 30-40 years if given the highest standards of care. They are a bit like tortoises, capable of reaching immense ages genetically, but physically, nutrition, breeding, parasites and bacteria take their toll on the average specimen. Thanks to bad keeping the worldwide average age for koi is probably only about 10 years.But basically, expect 30 years plus if you look after yours well. Standard goldfish, comets etc and shubunkins are capable of reaching similar ages. Fancy goldfish however generally dont get anywhere near that. Once adult, fish can only be conclusively aged by record keeping, or by a study of a spinal cross section, and the latter obviously requires the fish to be killed for it to be done.

On sexing the fish, adult females will be plumper, thanks to ovarian growth, and generally heavier than males, but this isnt conclusive. An experienced koi expert will get it right nearly every time, but for the rest of us mortals we just have to take our best shot at a guess.Before 10 months and reaching sexual maturity, sexing koi is nearly impossible.

I agree about the age of the koi. It could be very tricky which you would need to either examine through x ray or open it up. But actually according to what I read in one book and other sources, isn't the age determined by the annual rings on the scale?I know that is not accurate however its close enough. It would be similar human, each year we would grow at a certain rate except it may be variable. Isn't it true?

McCollum

Thsi only works if the fish are kept under conditions where the temperature fluctuates enough seasonally to affect the growth rates. The typical overfeeding and keeping them in warm temperatures that goes on will prevent scale readings from being accurate.Selective breeding also means that many koi do not have a normal keratin deposition, and as such scales no longer grow at the accepted norm. You might not get any growth marks in some years, and others you might get two or three. With most koi, aging them is pure guesswork. I guess what you could do is give them a guessed "biological age" based on overall condition. Basically if the fish is in superb condition , the age is really irrelevant. You not catch me turning down the offer of a big , mature, $4000 koi in glowing condition. It would probably outlive me!