Once known as the Taisho Sanke, or Taisho Sanshuko, koi of the Sanke variety look very much like Kohaku that have been spattered with ink. As a matter of fact, the two varieties, Sanke and Kohaku, are closely linked and are the only koi varieties with traceable bloodlines. Exactly when Sanke first appeared is open to debate, but it is known that a Sanke was first exhibited at the Tokyo Exhibition in 1914 by koi breeder Gonzo Hiroi. This would suggest that the variety may have been discovered in the late 1900s (which would place it in the Meiji era). Whether the Sanke was bred consciously or not is still unknown.
In the same year - 1914 - white koi with red and black markings appeared spontaneously in a brood of Kohaku belonging to Niigata rice farmer Heitaro Sato. Attempts to replicate the event were disappointing, and the three parent fish were passed to another breeder before being acquired by Eizaburo Hoshino of Takezawa - the village known as the birthplace of Nishikigoi. In 1917, Mr. Hoshino crossed one of these female Kohaku from Sato with a Shiro Bekko. The resulting fry showed the three characteristic Sanke colors in more or less equal proportions, with added sumi stripes on their pectoral fins.
However, the breeder who stabilized the strain was Torakichi Kawikame. He spawned a female Hoshino Sanke with a Yagozen Kohaku and the bloodline became known as Torazo, the name of Kawikame's father and the family business.
Today, most Sanke are the product of Torazo and the unrelated Sanba strain, which has since died out. The most famous current bloodlines are Matsunosuke, Jinbei, Sadazo and Kichinai.
Matsunosuke Sanke are the joint triumph of Toshio Sakai, who runs the Isawa Nishikigoi center, and his elder brother Toshiyuki, based in Niigata. The bloodline has been reinvigorated with Magoi genes to maximize growth, while retaining quality hi and sumi pigmentation. These koi, slimly built when young, are increasingly showing Fukurin scalation, which imparts a unique sheen.
What to look for in a Sanke...
A Sanke looks like a Kohaku combined with a Bekko. The hi should be deep and even, and well balanced when viewed without the sumi. On the other hand, the sumi should also be well balanced when viewed separately and should not extend below the lateral line. All the markings should have distinct edges separating the colors and the skin, which should be a snowy white.
Depending on the positioning of the sumi, it can be termed differently. Sumi that overlaps the hi is called kasane sumi whilst tsubo sumi is black on white skin. The latter is preferred more than the former, yet a combination of the two sumi types is most commonly found. Technically, Sanke are not supposed to have any sumi on the head but if the body of the koi is well patterned, pleasingly placed sumi found forward of the shoulders is not seen as a fault.
As with Kohaku, all of the fins on Sanke should be void of hi, but sumi on the pectoral, dorsal, or caudal fins is a desirable characteristic. The sumi found on the fins is a way of identifying the koi as a Sanke. If the sumi forms stripes on the fins it is a Sanke, as opposed to motoguro (blocks of sumi at the base of the fin) which points to Showa.
Sanke with a separate patch of hi on the head accompanied by more on the body are known as Maruten Sanke. If the hi is only on the head the koi is judged as a Tancho Sanke. Furthermore, if there is no tsubo sumi(black on white) at all, the koi is considered either a Kawarimono or Koromo.
Young, high-grade Sanke are easily confused with Kohaku. Sometimes sumi is not discernible until the age of two. Nor is there a guarantee that once the sumi is there it will be stable; it may fade again, only to reemerge later. Early sumi may appear as a faint blue-gray and will gradually deepen as the koi ages. Stable sumi that appears at an early age is called moto sumi, while black markings that appear later are known as ato sumi. Be wary of "windows", or white patches inside blocks of hi. This suggests that the koi may later lose its red patterning altogether.