KOI GENDER

On Thursday, November 20, 1997 10:00:00 AM UTC+2, brett rowley wrote:
In
(Ltbolt01) writes:

Could someone please tell me how to determine the Gender (sex) of Koi?
i have ten of them and i am curious as to which is which, and if i
have both
sex's so i can breed them.

Well, out of ten individuals, chances are you have both sexes present.
Koi will usually develop and show secondary sex characterisics during
the spring of thier second or third year. Females will usually be
plumper than males and have very smooth skin. Males will normally be
more slender and thier skin will become rough. Especially the head and
fins of males will feel similar to sandpaper as the water warms in the
spring. This is from protuberances common to the cyprinid (and some
other families of fishes)family called "nuptial tubercles". Some male
cyprinids, such as fathead minnows have tubercles that are very
pronounced, resembling horns on the face. Hence when they are ready to
spawn, they are "horny".

Sexually mature koi that are in spawning condition can be "milked" to
see if they are producing milt or eggs. This exercise is better left
to somebody very familiar with the procedure as it is easy to damage
the internal organs of the koi if they are squeezed too hard or in the
wrong place.

Koi will be stimulated to spawn by a combination of environmental
factors. They must undergo a chilling period of winter, then a gradual
warming period. After a certain amount of warmup and water temps of 59
degrees F or more, they can spawn. Other stimulating factors includes
a sudden increase in water level or improvement of water quality,
females exposed to males (especially if they have been kept apart all
year), a full moon during a warming period, the presence of suitable
spawning substrate, and perhaps many other factors. If the koi are
near to spawning condition, they can be artificially stimulated to
spawn through the use of some hormones. Some of these commonly found
on fish hatcheries are HCG (Human or Horse Chorionic Gonadotropin),
LHrHa (Lutenizing Hormone releasing Hormone analogue), or carp
pituitary extract.

In most instances, if the water is good and both sexes are present, koi
don't need much stimulation to spawn. They will go at it early in the
morning with vigor and enthusiasm. As soon as spawning is nearing an
end, they will immediatly begin to eat up all the recently laid eggs.
The use of substrates such as air conditioner filters, bus seat
stuffing, hyacinth roots, spanish moss, etc. helps to protect the eggs
and the substrate can be moved to a hatching container away from hungry
parents.

Rearing is the toughest part of trying to breed koi. The young koi are
very specific as to water quality and diet. To get any chance of
having a good baby appear from a spawning, many of them need to live.
We will usually feed the newly hatched larvea a mix of very hard boiled
egg yolk and powdered milk for the first three days. Then the young
koi are moved into especially prepared and fertilized rearing ponds
that have a lot of zooplankton, especially rotifers for them to eat.
Usually stocking about 100,000 to 250,000 per acre of rearing pond
(about 1/2 to 1 acre of rearing pond space per one female's worth of
fry). If everything goes well, and the breeding stock is of the
highest quality available (good ones are costly, $10,000+ per fish), a
dozen or so tategoi might result, the rest running the gamut from low
grade koi down to fish bait. Getting a good baby is like hitting the
lotto. To do so, you must either be very lucky, or buy enough tickets
to garauntee a hit (make enough of the babies live that the few good
ones are in the batch). I used about 15 acres of ponds this year for
rearing purposes. There is a lot more to do after the young are in the
special rearing ponds, such as feeding, fertilization, applying diesel
oil to the surface every couple of days, etc. etc.

There are a few good books on fish breeding applicable to koi. A
recent publication from Israel is pretty good, if very technical. My
best cookbook doesn't even mention koi, but is a text for use in third
world countries for growing carp to eat. It is called "A hatchery
Manual for the Chinese, Common, and Major Indian Carps" by Jingrin and
Pullin, published by ICLARM (International Center for Living Aquatic
Resource Management) in The Phillipines. Available at any college
bookstore where there is a fish culture program or through The American
Fisheries Society.

Sorry for the length, a very involved subject,

Brett Rolwey
Fisheries Biologist
Brett's Fish Farm
Liverpool, Texas

Louis Fourie.Hi Brett

I would like to know why the diesel or oil on the water and hoe do you feed the then.
For me yellow egg yokes work, but even better is growth food put dry in a coffee grinder or juicer to make it very fine

wrote in message...
brett rowley wrote:
(Ltbolt01) writes:
Could someone please tell me how to determine the Gender
--- (sex) of Koi? ---
Koi will usually develop and show secondary sex characterisics during
the spring of thier second or third year. Females will usually ---
Sorry for the length, a very involved subject, ---
I would like to know why ---

Neat!! Very interesting.
Thank you for posting.
(I'll admit, I do not know where this came from,
or where it is headed to,, but certainly a worthwhile
read on this quiet newsgroup!!)