How to identify male and female koi fish
Fins ď‚´ One of the most obvious differences between male and female koi of any age is the fins. Fins on female koi generally are less colorful than those of the males. Female koi fins also tend to be larger. The edges of a fins on female koi are more rounded and more opaque than the fins of males. The fins on the male koi have a more pointed appearance and tend toward more solid coloration. Photo from http://www.koi-fish.com
Female koi fins
Male koi fins
Size ď‚´ Female koi are, in general, larger than their male counterparts. That aspect of their physiology is the result of selective breeding to protect the females when put in with groups of male koi. In other words, koi breeders would usually put one female with a group of males to create a more diverse gene pool. In order to protect the female fish from injury, they used larger females and smaller males, and those traits were passed on to their offspring.
Photo from sunlandwatergardens.com
Shape ď‚´ There are definite shape differences in adult koi based on the gender. However, those differences are not as apparent in the young fish. That's because it's caused by the eggs carried by the female koi, which don't develop until maturity. In general, male koi have a narrower, sleeker appearance. Female koi, on the other hand, are shaped more like a blimp with a more rounded body. That shape is caused by the eggs that they carry.
Vent Male - elongated or triangular in shape, sunken and concave, Female - more round in shape, protrude and convex, a more prominent and long transverse ‘slit’ running across, blush of red color around its perimeter
1. Vent 1 (Confirmed female) Reason for female?? : more round in shape and a more prominent and long transverse ‘slit’ running across (shown by the red arrow) pictures I have taken from Koi-Bito and Koiquest
Female
2. Vent 2 (Confirmed male) Reason for male?? : elongated in shape, sunken and concave
male
3. Vent 3 (Confirmed male since got milt) Reason for male?? : Triangular in shape?? Most people would have sex this koi as female since the vent is a bit protruding and red (I suppose he was heavily fed)
male
Telling the Difference: It is much easier to tell the differences between sexes when Koi get larger and older. When they reach sexual maturity, at around 2 years of age and around 12" of length, the females will fill up with eggs. This will give them the blimp look. When Koi are larger, it is easier to tell if their fins are pointed or rounded and if they are clear or opaque. If you like my video, hit like, share and don’t forget to subscribe Thank you.