Shiro Utsuri

 Quick Care Facts

• Care Level: Moderate   • Temperament: Peaceful   • Maximum Size: 28 to 40"
• Minimum Tank Size: 500 gallons   • Water Conditions: 55-79° F, 34-85° F temporary water conditions
• Diet: Omnivore   • Origin: Japan, selectively bred carp   • Family: Cyprinidae
• Species: Koi, Nishikigoi/錦鯉 (Japanese)   • Aquarium Type: Pond

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Shiro Utsuri have a very long history that dates back to the early 1900's where they are believed to have been first produced by Kazuo Minemura sometime around 1925. Their contrasting black and white pattern made them a very attractive variety who were instantly sought after by Koi enthusiasts.

Early Shiro Utsuri did not grow as large as the other popular Koi varieties of the time, which prevented them from doing well in Koi shows and limited the overall potential of their beauty. This disadvantage was erased when the Omosako Koi farm began breeding Shiro Utsuri that in time reached lengths over 40 inches in size, which not only brought out the full beauty and potential of the fish but also allowed them to win awards at Koi shows including the All Japan Koi Show.

Shiro Utsuri are most often confused with Shiro Bekko, but by applying the same criteria that differentiate Showa from Sanke, the difference becomes clear. A Shiro Utsuri is a black fish with white markings, a Shiro Bekko is the reverse, and all Utsuri sumi (black) is of the typical Showa "wraparound" type, which extends down to or beyond the lateral line on the side of the fish.

The following traits are essential for quality Shiro Utsuri Koi specimens:
 
The sumi (black) should ideally be a jet black color with a glossy sheen, similar to that of a Showa Sanshoku. To best inspect the quality of the sumi, view the fish in good daylight, and look for the sumi to maintain a deep black color. If the sumi takes on a brown-black or gray-black appearance in bright sunlight, then this is considered lower quality and a fault in show judging.
 
Head patterning of Shiro Utsuri can range from the classic lightening strike or V-shape similar to that of a Showa, to relatively small counterpoints on the white skin. These don't have to be symmetrical, but the edges should be clearly defined. Too much black on the head, especially if there are several small patches rather than a continuous pattern, makes the Koi a lower quality specimen.
 
Similar to how a Kohaku is judged, Shiro Utsuri are classically simple, two-colored Koi. Therefore, a great emphasis is placed on the quality of the white skin. This should be the color of snow with a healthy, yet subtle sheen.
 
The pectoral fins should not contain too much sumi (black), but should instead have a neat motoguro on the pectorals. Essentially the white on the finnage should set off the body sumi. Dorsal and caudal fins are allowed some sumi, but again, if there is too much, the Koi will appear unbalanced. Ideally, Shiro Utsuri, like Showa, should display the same classic motoguro on their pectoral fins, and as modern tastes for white predominance has become popular in the hobby, more white than black on the fins is a good way to go.
 
Sometimes the skin of a young Shiro Utsuri will give few clues as to how the finished Koi will look. The most common "fault" in yearling Shiro Utsuri is a yellowish head. This is interpreted in a number of ways, with some seeing it as a sign that the fish is male, or that it will grow into a quality Koi, though some examples never quite lose this tinge. Similarly, the white on the body can appear rather dingy, this means that there is sumi still to arise give the skin a bluish gray tinge. It is said that the best way to tell to how the finished Koi will look is to examine the white at the base of the tail, which clears sooner than the rest of the body.
 
When choosing young Shiro Utsuri, steer clear of fish that look like miniature versions of the ideal adult. More sumi will almost certainly come later, making the Koi too black heavy.
 
Water chemistry in which Shiro Utsuri Koi are raised can influence how they look. Specifically the sumi (black) develops best in hard, alkaline water, but in softer, more acidic ponds it takes on a gray or blue tinge.

Caring for and keeping Koi is tightly tied to the pond in which they live, as the keys to successful Koi keeping revolve around water quality, proper filtration & aeration, quality food and protection from predators. First things first when keeping Koi and that is simply that they get big and need a pond to match. Depending on the number of Koi one plans to keep they need to build a pond that is up to the task of keeping a group of 24" to 30" on average fish that can reach a body mass nearing 30 lbs! While bigger is better, a few rules that will provide a good minimum starting point for an adequate Koi pond include the pond being at least 4 times the length of an adult Koi and 3 times the width, with a depth of around 3 feet. While modern filtration can keep fish alive in very small amounts of water, some reasonable swimming space is required for such large fish and they need some depth to be able to regulate their temperature by swimming closer or further from the surface of the water depending on temperature.

Koi like their common carp ancestors are a cold water fish capable of living in temperatures ranging from the mid 35° F to 84° F they are considered a hardy fish species. However, Koi do not do well if kept at extremely warm or cold water temperatures for long periods of time. They prefer water temperatures ranging from 50° F to 78° F (10° C - 25° C), where they are in ponds that are deep enough for them to regulate their body temperature as they see fit by swimming higher or lower within the pond. The exact ideal depth for a pond depends greatly on the climate where the pond is built, warmer climates can have ponds as shallow as 3 feet in depth, where colder climates will need at least 5 feet deep areas to allow the fish to survive cold winters.

While Koi are fairly hardy fish in general they are selectively bred over hundreds of years for color and pattern, which has made them less hardy than their native carp cousins. Koi are especially sensitive to low oxygen levels and high levels of nitrate in the water. Therefore, proper pond filtration is critical to maintaining high quality water which is crucial to Koi health and longevity. Proper Koi pond filtration should provide high levels of dissolved oxygen, excellent mechanical, biological and chemical filtration and provide parasite control via a UV sterilizer. Partial water changes or the use of plants as a vegetable filter should be used in order to export or remove nitrate from building up in the water.

Second only to the pond design and water quality, Koi need high quality foods that provide them a mix of meaty and plant based food items that will provide a balanced and nutritional diet. Koi should be fed different foods or not at all based on the water temperature and time of year. In the Spring and Fall where water temperatures are between 55° F - 68° F (12° C - 20° C) Koi should be fed foods lower in protein and more easily digestible. When water temperatures are above 68° F or 20° C, then can be fed higher protein foods.

The pond design is also critical in terms of protecting Koi from predators and harsh water temperatures. Ponds that have gradual sloping sides and are shallow in depth allow predators to easily wade into the pond and feed on the Koi within. Also shallow ponds, especially those without shade provided by pond structures or overhead vegetation make it difficult for Koi to avoid the intense sun and high water temperatures during summer months. Koi ponds should have sheer edges that drop down quickly to 2 to 3 feet in depth to deter predators and should have areas of the pond that are deep enough to avoid predators and excessive winter or summer water temperature extremes.

Koi being bred from Carp are an omnivorous fish species, who with their down turned mouths typically eat food items that they scavenge for on the bottom of their natural pond, lake or river homes. However, as Koi are selectively bred in captivity and raised in well maintained ponds, they have adapted to eating food from the surface of the water and will readily consume a wide variety of commercial floating foods designed for Koi.

Many Koi keepers prefer to feed their fish at the surface of the water as it allows them to bond with the fish by training them to hand feed and gives them a chance to inspect the fish for any signs of disease or any wounds brought on from pond predators like raccoons, herons or foxes.

Koi will readily consume a wide variety of natural foods in addition to balanced commercial Koi foods, these include: lettuce, watermelon, peas, oranges, squash and fresh seafoods like prawns, shrimp, scallops, squid, chopped fish, mussels, etc. as long as it is fresh and not pre-cooked or preserved in any way.

Koi should be fed different foods or not at all based on the water temperature and time of year. In the Spring and Fall where water temperatures are between 55°F - 68°F (12°C - 20°C) Koi should be fed foods lower in protein and more easily digestible. When water temperatures are above 68°F or 20°C, then can be fed higher protein foods. In the Winter when water temperatures are below 50°F or 10°C, the digestive system of the Koi will slow nearly to a halt and they should not be fed directly, they may nibble a little on plants and algae, but won't need direct feeding.

Feeding Koi when the water temperature is below 50°F or 10°C runs the risk that any food eaten may not be fully digested and will rot inside the gut of the fish causing illness and possibly cause the Koi to die.

Koi, just like standard Carp when bred naturally will spawn in the Spring and early Summer. Spawning is initiated by the male who will begin following the female about the pond, swimming right up behind her and nudging her repeatedly. After the female Koi is stimulated and releases her eggs, they will sink to vegetation, spawning mobs or even rocks or gravel on the bottom of the pond. The male will release sperm into the water and the eggs will become fertilized and begin developing. Although the female produces large numbers of eggs, many of the fry do not survive due to being eaten by other Koi or because they are not properly fertilized. On average if the egg survives it will hatch in around 4-7 days.

Most pond keepers looking to spawn their Koi will use mop heads or specialized Koi breeding mops in order to be able to control where the eggs are hatched. Since Koi will produce thousands of offspring, of which only a small percentage will carry the proper coloration and pattern necessary to be considered Nishikigoi or Koi. The rest of the offspring will be brown, black, grey or mottled in color and have little to no real color pattern. Professional Koi breeders will cull these undesirable offspring and only raise up the fish that show the desired coloration and pattern.

Nurturing and culling the resulting offspring or "fry" as they are known is a time consuming and tedious job, typically only done by professional Koi breeders or farms. The difficulty in raising quality Koi is in the continual process of feeding, sorting and culling the fry for months on end, while also needing to continually move desirable fish to new and larger holding ponds as they are grown out. Koi breeding at a minimum requires maintaining multiple grow out ponds, having many different types of foods on hand (including live or frozen foods) and performing sorting and culling duties every few weeks for the first year or up to about 6 inches in size. The resulting "Tosai" or yearling Koi will vary in quality from lower pond grade all the way to varying levels of high quality Koi.

While quality parent fish, high quality water conditions and foods provide reproductive advantages for Koi breeders, the semi-randomized results of the Koi reproductive process means that it is possible to get a favorable result even for novice breeders. Additionally the variability in the reproductive process allows for new varieties of Koi to be developed within a relatively few number of generations.