Using scale rings to age fish is a valid method. But in that case it was taken completely out of context.
First, you don't count the number of rings on the scale, that has no bearing on the age of the fish. You carefully analyze the scale under a microscope and look for signs of years passing. Its not the number of rings, but it does involve using the rings.
Second, you do this on many fish from a group sample to determine individual cohorts (year classes). Scale data is combined with indexes like length x frequency distribution, relative weight, relative abundance, etc. to set ages of individuals and groups. Wihtout the corraberative data and many data points from many fish, the method has little value. This case of one koi in one pool is such a case.
I was trying to think about my older koi. I've got only a few left from the original group brought from Japan in '92. So some of the koi are at least close to 20 years old.
For the purpose of operating a business, I asked Japanese breeders about breeding stock. Breeding koi are depreciated over five years for tax purposes. On average, the loss rate of breeding stock is about 20% annually. This means that the average brood koi has an effective life span as a breeding animal of five years (nine or ten years old).
Brett
03-14-2008
), and I cannot recall any from other threads. JR's points are instructive. There are relatively few hobbyists whose ponds would promote full life spans. And, as Tony points out, many of those few will move on a koi that begins to decline... very frequently to one of the lesser ponds. Brett's doitsu Sanke brings to mind that breeders may be more likely to have an old gosanke around, retired from breeding days. Spawning can be hard on the females, but no koi will be as carefully attended year-round as the breeder's oyagoi. But, not many 20+ year koi breeders outside Japan. ...Hmmmmm.
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