Japanese koi fish: A suitable candidate for backyard ornamental fish farming in Manipur

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Written by : Dr. Chimwar Wanglar, Ms. Soniya Laishram, Dr. Nilachandra Thangjam, Mr. Suraj Kumar Irungbam, Dr. Bedajit Yumnam, Dr. Dipak Nath, Dr.Angam Raleng, Prof. Ratan Kumar Saha and Prof. Phurailatpam Ranjit Sharma

Introduction: Nishikigoi/Japanese koi/Koi, a mutant variety of Cyprinus carpio (puklaobi) fish, is one of the most expensive and popular decorative fishes in the world. Koi are unique multicolor fish and multiple color varieties have been developed since the early 1800s in the Niigata province of Japan.

It is believed that koi varieties were descendents of Magoi (black carp) variety, which were cultured as food fish in China and transported to Japan around 1000 AD. In the early 1800s in Japan, colorful patterns and varieties of this fishes were observed and selectively bred for these characteristics which gained extreme popularity.

Koi were first introduced to the USA in early 1940s while koi were not seen in Great Britain until the 1960s. Since then koi keeping and breeding has gained worldwide following in Asia, Europe, South Africa, etc. Generally, Koi are 30 to 60 cm long and have a typical life span of around 40 years, though the oldest-known koi (Hanako) lived to be 226 years old.

In 2018, the most expensive koi was sold at about 1.8 million US dollars. It was a 3 foot koi name S legend kohaku variety. The value of each Koi fish is based on the specific color pattern, size, body conformation, intensity of the color, etc. However, most of the koi color types are not true breeds i.e. the patterns are not repeatable. Koi farming depends largely on strict and continuous culling throughout the culture period making it expensive to obtain a particular breed or line.

Although most koi around the world are Japanese origin, however, there are differences in quality between the domestic (other countries) and the Japanese breed. Japanese koi breeders have been producing koi for generations by rigorous culling to maintain a gene pool of high quality koi. Generally, it is believed that the highest quality Japanese koi is never exported to other countries. Koi breeders around the world focus more on faster growth and early breeding to generate mix varieties that are generally cheaper.

Domestic Koi Fish Japanese Koi Fish

Bred from mixed varieties of koi Japanese bred from ancient varieties of koi (generally breed and maintained for several generations) breed when the fishes attain as early as 1 year Breed generally when the fishes attain 4 years
Higher fecundity Lower fecundity
Faster growth rate Slower growth rate
Concentrate on the mix varieties Concentrate on few varieties to achieve high level quality breed/line
Smaller size ( 12-15 inches on average) Larger size ( up to 36 inches)
Sold generally at any size and age and not intended for auction Mainly for auction and to be sold at higher prices
Affordable for all enthusiasts Expensive
Shorter lifespan (15 years on average) Longer lifespan (commonly reaching 50-60 years)
Easier to keep in an aquarium Generally cultured in big ponds

Common varieties of Koi:

Currently as many as 120 different koi varieties are distinguished and the most popular category is the Gosanke (Kohaku, taisho sanshoku, showasanshoku), Tancho, Chagoi, Asagi, Bekko, Ogon, Kawarigoi, etc. Other new varieties such as Ghost koi, Butterfly/Hirenaga/longfin koi, though they are not considered true Nishikigoi. Some common varieties are discussed below.

Kohaku indicates “red and white” and these fishes have white background with red markings across the body.
Taisho sanshoku otherwise known as Sanke koi are similar to Kohaku but have additional black markings on their body.
Showa sanshoku or Showa are black koi with red and white markings on the body. Recently, the amount of Sanke has increased and can be difficult to distinguish from Showa.
Bekko are white, red or yellow background with black markings in the body.
Tancho is any koi with solitary red patch on its head.
Kawarigoi are koi that cannot be put into any one of the major categories.
Kohaku Sanke Showa Bekko Tancho Butterfly

Reproductive biology: The age of maturity for breeding of koi varies from 1 to 4 years for both the males and females. They tend to mature earlier in tropical waters than northern parts of Europe and America. Once they mature, they tend to breed every year. Some breeders have managed to breed the kois twice per year, but the female koi will lay significantly fewer eggs in the second time around.

A matured female can release around 100,000 to 150,000 eggs per kg body weight of fish (domestic koi are found to spawn as many as 400,000 eggs per kg female).

However, only around 60% of these eggs will hatch and even fewer may have reasonable chances of becoming a fry. The best results are observed when the female is at least 4 years old and a male at least 3 years old. The reason being is that the female would be of a good size and in good condition which would let her carry many thousand large, quality eggs with a good yolk sac.

The larger the yolk sac the larger the fry and the quicker they will eat microscopic food so the faster they will grow. It is also an advantage to use a large koi of 4 years as they have better ability to cope with the many hours of the spawning cycle.

Breeding of Koi

Brooder selection : Koi females develop two large ovaries which take up major part of the body cavity. So, the first sign of readiness of koi females for spawning is the presence of a pronounced, round and soft abdomen. Males do not have enlarged abdomens and gentle pressure on the abdomen near the genital pore will release milt/sperm that is white in color. Both the male and female fishes have to be weighed to calculate the appropriate amount of hormones for injection.

Female Koi Fish Male Koi Fish

Body shape Shorter and rounder body Longer and slender body
Pectoral fins Rounder, almost translucent Pointy, opaque, intensely colored
Vent appearance (anus) Transverse slit running across the slightly protruding vent Rounder vent

Physical changesduring mating Will become rounder and chunkier. Will develop sandpaper-textured white tubercles on the side of their face and on their pectoral fins.

Breeding management : Breeding of koi fish can be done in both natural and artificial ways in confined waters like tanks and ponds. It is essential to provide some substrates which may be in the form of roots of water hyacinth, plastic straps, nylon filaments, etc., to help the sticky eggs to adhere and for easy collection of the eggs. The male and female brooder fishes are to be kept separately, at least two weeks, before breeding them and fed with protein rich formulated diets with some treats in the form of tubifex worms, mealworms, redworms, insect larvae, etc., for faster gonadal development.

Koi are omnivorous feeders and will eat food found at all depths of water. High carbohydrate feeds should be avoided to prevent deposition of fat. Avoid overcrowding and stress while netting. Spawning is triggered by factors like temperature, water parameters, pH, etc. Optimum temperature for breeding of koi is 18 to 22oC and pH of 7. Fluctuation in pH is not suitable for koi breeding.

The Dissolved Oxygen should not be less than 5ppm (mg/l). The ammonia level should not exceed 0.05ppm. It is not advisable to feed the koi while they are in the breeding tank. The tank should be filled with treated, fresh water of pH 7 to 7.5 and if possible the water temp should be 5o C below the main pond temperature.

This helps stimulate the females andmimics the natural habitat. Brooder fishes should not be kept in the breeding pond/tank for more than 4 days.

Natural breeding: Similar to common carp, Koi fish can breed naturally in tanks and ponds under optimal conditions.

After the brooders are introduced into the breeding tanks, a short “courtship” play can be seen day before the female lay eggs where the male koi will follow the female and bump into her intentionally for an entire day till the morning pushing her towards the more dense substrate areas of the pond/tank. When ready, the female koi will willingly move to the corner and release the eggs.

As soon as the female lays the eggs, the male koi will start to release sperm onto the eggs. This entire process can make the water inside the tank/ pond look extremely cloudy. Laying of eggs generally last for 2-3 days.The sticky eggs will be attached to the provided substrates.The sticky eggs can be collected and transferred to hatching tanks.

Artificial breeding using inducing hormones : Koi can also be induced to breed using commercially available synthetic hormones such as Ovatide (Gonato-trophin Releasing Hormone and dopamine antagonist), Ovafish (Salmon GnRH), WOVA-FH, etc., or by using Carp pituitary extract (Cpe). The dose of synthetic hormones is 0.1 to 0.2 ml/kg body weight (b.w.) for males and 0.4 to 0.5ml/kg bw for females and injected as one-time dose.

However, while using Cpe, the females are injected two doses. A preliminary dose of 0.35 to0.45 mg/kg body weight (b.w).is injected as a preparatory dose and followed by a secondary dose of 3.5 to 5mg/kg b.w.for the females with an interval of at least 7 to 8 hrs between the two doses, depending on water temperature. The interval may take as long as 11 to 12 hrs at 21 to 22oC. Some of the literature also suggest higher doses of 6-12mg (10-30% as preliminary dose and 90 to 70% as secondary dose).

For male fishes, a one-time dose of 1.5 to 2mg/b.w. is given during the time of injecting second dose to females. Fishes are extremely flexible so different doses and different ratio for first and second dose or different protocol may be required. The injected fishes are released into the breeding tanks/ponds. Breeding tanks should be covered in nets to avoid the fishes from jumping out. Spawning starts after 5 to 7 hrs of second injection. The fertilized eggs can be transferred to hatching tanks. If the brooders have not spawned in that time, the fishes should be taken out and new pair can be injected.

Hatching of eggs: Fertilized eggs are transparent with light yellow or brown in color and embryonic development generally takes 3 to 5 days at 21-22oC. Mass hatching takes place during the 4th to 5th day. The spawn/larvae of koi do not have pigmentation in their bodies. Hatchlings are transparent and with round yolk sac. Once the yolk sac is absorbed after 3 days, exogenous feeding should be given after that.

The spawn can be fed zooplank-tons, brine shrimp, chopped tubifex worms, commercial powder feed,etc. After two weeks, pigmentation of the body will start and color combinations can be seen. Keeping the larvae in intensive system/tanks for a short period of time has proved more efficient than the direct storage of the larvae in the ponds.

Culling : Nishikigoi do not “breed true” and always require severe culling during the first culling to maintain true due to the variety’s constrains. For example, when a Kohaku variety is bred with another Kohaku variety, at least 60-65% of the off springs are removed at about 40 days of age.

Likewise, 75-80% of a Sanke cross is removed at first culling at 25-30 days of age. At least two more culling operations are carried out before the age of six months illustrating how much value is placed on the individual gene make-up. Intentional hybridization and line breeding lead to improvement and proliferation of varieties while stringent selection and culling regime led to increase in quality and marketability of the variety.

This is labor-intensive and requires skilled people, which are few and limited outside of Japan. In countries like Taiwan and perhaps a handful of dedicated producers around the world follow the culling tradition to improve their production. As for most breeding outside Japan, the resultant breeding is without purpose other than for a multitude of small, colorful fish compromising the “quality” of koi.

Conclusion : Nowadays, in the US and other Asian countries, several domestic breeders no longer import brooders from Japan but have improved their techniques through years of experience. In India too with the rise in number of koi hobbyists, many are interested in breeding and maintaining different varieties of koi based on their preferences. Unlike the auction tradition in Japan, the smaller mix varieties of koi which have faster growth, higher fecundity and cheaper/affordable price also have huge market.

Nishikigoi are easy to breed in confine waters and a suitable candidate for backyard fish farming especially for unemployed youths and women and can be a good secondary source of income for their livelihood. Koi carps are also good candidates for sport fishing and this technology can be used to attract many recreation clubs to introduce this fish in their ponds and lakes.