Dry Method of Koi Fertilization (Hand-stripping)

One of the nicest surprises that a pond owner can receive is to unexpectedly see hundreds of new baby koi swimming in his or her pond. Many koi hobbyists become fortunate enough to experience this, thanks to the fact that koi are very prolific breeders and will spontaneously spawn in any pond under the right conditions.

Still, given the awesome fecundity of koi, their natural reproduction in a pond is not as commonly encountered by koi hobbyists as should be. The primary reason for this is that koi love eating their eggs and larvae. As such, their young seldom grow big enough for a pond owner to see. People who want to produce their own koi fry, therefore, can not rely simply on natural reproduction in the pond. To increase their success in producing koi fry, they need to mimic the natural reproduction of koi under more controlled conditions using the basic method for breeding koi.

One disadvantage of this old method for breeding koi is its dependence on the cooperation of the koi being bred, i.e., the female must be induced by the male to lay eggs and the male should be able to fertilize these eggs.

A more dependable method for koi production is known as the dry method of fertilization. This method induces the female and male koi to release their eggs and sperms, respectively, through 'hand-stripping' under dry conditions (which is how it got its name). The steps employed for the dry method of koi fertilization are as follows:

1. Collection of the Female's Eggs. Put the ripe and ready-to-spawn female koi in a small container that's filled with a tranquilizing solution (e.g., 100 ppm Benzocaine). The transfer must be made very gently using a soft net since the koi is heavy and can be easily injured out of the water. The tranquilizing solution anesthesizes the female koi.

Once it is calm enough, take it out of the water carefully and wipe it gently with a soft towel until it is dry (see Figure 1). The female koi must be dry prior to being stripped of its eggs because the eggs will pre-activate if it comes into contact with water before they are fertilized. A helper must clog the genitals of the koi to prevent it from releasing eggs prematurely during this procedure.

Figure 1. Prior to hand-stripping, the koi must first be dried with a clean and soft cloth.

After the koi has been dried, it is ready for hand-stripping. To do this, gently massage and squeeze the swollen belly of the koi while holding it over a dry, clean bowl. The gentle squeezing will cause the female koi to release its eggs in the form of a brownish fluid, so make sure that when this happens the fluid will fall directly into the bowl to avoid spillage (see Figure 2).

Figure 2. Collect the eggs of the female koi in a dry, clean bowl during hand-stripping.