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Pond & Garden Science: Grading Koi

07/06/2017 0 Comment(s) Pond & Garden,

Author: Leslie Tsen (B.S.) Ecology, Evolution & Natural Resources. Wildlife Conservation

Koi fish are regarded as some of the most expensive ornamental fish, but their price can vary greatly depending on their grades. Grades given by reputable breeders and companies will often determine the class and status of the Koi fish being sold. As beauty is highly subjective, even the grading system varies between common Koi breeders and distributors, making it difficult to judge the quality of a Koi based on beauty alone. As a result, hardcore Koi fans nowadays follow a more standardized Koi grading system known as the Sembetsu, a traditional Japanese Koi grading system that requires highly skilled and experienced inspectors to make careful examination on each aspect of the fish.


Modern Grading System


Modern grading systems that are commonly practiced by distributors or breeders tend to be preference based rather than guideline based. Koi distributors or breeders will first sort out their Koi types and breeds, then price them according to general preferences following the demands of the public. Some may even assign alphabetical letters to justify the quality of their Kois, ranging from the average C-grade to the highest AAA-grade. The nominal classification uses three major categories to represent Koi’s standard: the “standard”, “select” and “premium” quality, with “standard” being the most common grade, “select” being the average grade, and “premium” being the highest level grade. It is important to note that any grading of Koi that follows no strict guideline is almost always highly subjective. A Koi that looks like a “premium” to me might very well look like a “standard” to you. As long as you are satisfied with your Koi, all Koi are of the highest quality.


The vast amount of Koi grading systems have led many to refine and simplify their grading standard using basic nominal categorial terms such as “low grade”, “middle-class”, and “high quality”. The term "low-grade" is commonly associated with ordinary domestic Koi that are widely accessible, 'Tosai' or less than a year old Koi, and those that are genetically less similar (eg. Cyprinus carpio x Carassius auratus hybrids) to the Japanese Koi. The term "middle-class Koi" tends to refer to those that are almost genetically similar to the Japanese Koi with very good colorations and body patterns, but Koi usually take two to three years time after hatching to develop full body pigmentation. Therefore, it is not uncommon to see lots of 'Nisai' and 'Sansai' Koi fall into this category. High quality Koi have distinct scale features, textures, and "fukurin" or unique net-like skin cuticles between scales which differentiate them from the rest. They also have a perfect body shape with beautiful skins that are translucent yet reflective and bright. These Koi are thought to be carrying the modern Japanese genetic thus are ranked the highest.


Traditional Japanese Grading System - Sembetsu


Sembetsu is a traditional process which is also considered an art form in grading Koi fish. This method takes its practitioners years or decades of experience to master the true art of Koi grades assessing. True experts in Sembetsu will grade the Koi in two ways: Choice grade that includes Koi with vibrant mixed of colors and patterns, and elite grade Koi which exhibit not just unique patterns and vibrant colors, but must also come with a perfectly shaped body.


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Disclaimer: This article contains materials referred from published scientific journals and is strictly meant for educational purposes only. It must NOT be substituted for any forms of medical care, treatment, and consultation from veterinarians, aquatic experts or other licensed professionals. NO compensation shall be reimbursed by Harvest Fish & Pet for the direct or indirect loss, damage, injury, or death of both living (user included) and non-living beings caused by the application of information from this article either in full or in part.  

Tags: science