【Professional Tips】Medaka Selection Techniques | How to Identify Quality Specimens
Selection methods for improved medaka varieties. Explanation of how to distinguish body iridescence, scale shimmer, body shape, and selection timing.
Key Takeaways
Selection methods for improved medaka varieties. Explanation of how to distinguish body iridescence, scale shimmer, body shape, and selection timing.
The Importance of "Selection" in Determining Improved Medaka Quality
In improved medaka breeding, selection (senbetsu) is one of the most important tasks. No matter how beautiful the parent fish you have, if you neglect selection, quality will decline with each generation. Conversely, by continuing proper selection, you can gradually produce ideal specimens from the fish you have on hand.
Selection is the process of sorting out specimens for breeding, specimens to release, and specimens to exclude. It's not simply "keeping good fish," but rather a strategic decision that determines the breed's direction. It may seem difficult as a beginner, but anyone can develop an eye for selection if they understand the key points. If you search for medaka from breeder direct sales, you can meet high-quality specimens refined through careful selection.
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Selection Timing by Growth Stage
The basic approach is to select medaka at each growth milestone. Rather than trying to sort everything perfectly at once, accuracy improves by narrowing down in stages.
Fry Stage (Hatching to 1 Month)
Selection during this period focuses on "exclusion." Early removal of deformed specimens—such as those with curved spines, missing fins, or significantly delayed development—is essential. Most deformities are hereditary; overlooking them and raising them to adulthood risks using them for breeding. Additionally, deformed specimens mixed in can hinder the growth of other fry.
Juvenile Stage (1-2 Months)
When body length reaches approximately 1-2 cm, breed-specific coloration and patterns begin to emerge. At this stage, check the intensity of body color and the direction of color development. While not yet fully expressed, this is when hints of future beauty begin to show. Specimens with weak coloration or off-target color directions are culled at this stage.
Young Adult Stage (2-4 Months)
This is the main selection period. Breed-specific characteristics—body iridescence, scale shimmer, body shape, fin morphology—are nearly fully expressed. Breeding candidates are narrowed down at this stage. Be especially careful when selecting parent fish for the next generation.