Wednesday, January 23, 2013

Sexing Koi - Is a boy or a girl koi?

Sexing Koi
Customers tell me it's one of the most frequently asked questions that they get. Is it a male or female?  While it can be difficult to differentiate the two, it's not impossible. Use these tips to figure out the sex of your or your customers koi.

1.)  The Shape
The sex of a young Koi does not affect its body shape until it begins to reach sexual maturity, which is usually at around three years of age. Most females at this age will start to carry eggs and will tend to be more rounded and "blimp" shaped. Males are more streamlined and torpedo shaped. Males lack the swollen abdomen of females. Generally speaking, females will grow to a larger size than males. Take a look at the pictures below for an example of the two. 

male and female koi
Click for larger images

2.)  The Feel
Generally by two years of age, male koi will start to feel rough to the touch, especially during the spring season as temperatures are rising. If you rub your fingers on the gill plates and along the side of the body, it feels like sandpaper. Females will be slick and smooth to the touch.

3.)  The Vent
The male vent will be more con-caved in appearance where-as the female vent will be convex and slightly protruding with a slight pink appearance.  Below are an example of the male and female vents.  Click on an image to see it in a larger format.
male vent
Click for larger image.
female koi
Click for larger image

4.)  The Behavior 
During the spring spawning season sexually mature males will chase the females, nudging them with their nose to encourage her to release her eggs.  

Randy LeFever
Blue Ridge Fish Hatchery

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