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

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
Contd from last Saturday
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.