Stupid Question Time....

[JasPR]

I'm a big old Japanaphile when it comes to immersing one's self in the study of nishikigoi. And as you may have noticed I purposely use the term Nishikigoi ( fancy carp) over the term koi when I want to stress that the identity of koi was created by the Japanese so the terms associated with the culture need to be understood. Kohaku just means red and white, however. And tosai just means 'in the first year of life'. So these harvest terms are charming but not very scientific. So for the true KOI student, the science is more educational/enlightening than the charm of Japanese terms.

It is very important to appreciate that fish go through huge physiological and behavioral changes that are best looked at like stages of life.
The stage right after hatching is more than just 'little koi' that don't need to be fed because they have yolk sacs. These larvae ( hatchlings) have NO mouth, No swim bladder and no gills! How could one call these the same name as the stage that will be actively hunting for food in the weeks ahead??
The fry is also NOT a miniature adult. It is a physiologically different creature. Its gut is short, its demand for animal protein is high, its skin is non-developed ( a thing that makes a nishikigoi a nishikigoi) and its behavior is very different from an adult.
The term 'fingerling' is usually a size description, I think. How can one call a tosai a fingerling when some tosai are now 12 inches?? That is a game fish or fish hatchery term in my mind? It is pretty hard to make it compatible with koi and their growth experience?
I see all koi moving from fry to young or juvenile stage. It is a young koi and as such, has juvenile qualities and shows juvenile traits of body, skin and color. It begins to swim differently than a true fry stage and browses rather than hunts. It is as distinct a change as a baby is to a child.

The biggest experience in koi development as living art is sexual maturity. The body line changes and the colors change. The skin changes. And at the heart of these things is a change in hormone levels. So this is not only a change in judging approach at the koi show, it is a change in husbandry approach as well. This fish has become a true omnivore and the gut is now proportionally 5 times the length as when it was a fry. So it can browse all day and fill that long gut with a vriety of food fuels. It is also a fish of deep water now. No longer a fish living in the margins hunting live food.

As you might know, I'm a BIG fan of seeing koi as 'four season' fish. Beyond the charm of this Japanese perspective on the carp, there is a real underlying science. Very cool when folklore and hard science blend.
I also see the life stages of koi as producing 5 distinct creatures over time. And each of 'these creatures' must cope with 'four season identity' in a different physiological way.
- JR

[KoiCop]

Nice post.

At what age &/or size do fry begin to transition to the juvenile stage?

Thanks,

[JasPR]

Hi Don, thanks. I never really focused on exactly when a fry should be more properly referred to as a juvenile? Still, rather than length, age or weight, I'd look to development.
I guess I would be comfortable calling a fry a juvenile koi when it was fully developed physically, putting energy into Growth (length) and but not yet putting energy into gonad development. This has no scientific basis as an indicator, but when things like the 'brain case' close ( that black shadow on the skull that allows one to see into the skull) and skin evolves to expanded layers, colors begin to deepen etc., I think of that fry as a young koi.

JR