Artificial insemination and production of fry of tangra fish in Bangladesh
Tangra is one of the freshwater fish. The fish is very tasty, rich in beneficial nutrients for the human body and is loved by everyone as it is less cut. At one time the fish was found in abundance in inland water bodies but the abundance of this fish has decreased due to destruction of habitat and breeding grounds due to various reasons like application of pesticides in crop fields, construction of unplanned dams, drying of water bodies, discharge of various industrial wastes etc. In order to save the species from extinction and to ensure the availability of pona for cultivation, it is very important to invent artificial breeding, nursery management and farming techniques of tangerine. Scientists have already succeeded in inventing artificial insemination of fish, fry production and fry rearing techniques by conducting research in the freshwater sub-center of the Bangladesh Fisheries Research Institute, Syedpur, with the aim of increasing the conservation and production of the species.
In the drought prone Rangpur region, most of the water bodies have water for 5-6 months and there are many shortages in fish production in this region. Ensuring the availability of tangra pona through artificial insemination and storing it as an alternative to other fishes under seasonal water farming will improve the socio-economic condition of the rural population along with increasing fish production in the region.
Characteristics of tangra fish
Tangra fish is of special importance in terms of economy, taste and nutrition.
The following are the characteristics of this fish:
- Helps to increase the income of hatchery and pond owners.
The essential nutrients and micronutrients for the human body exist. - Can be cultivated in small and seasonal water bodies with easy management.
- Buyers prefer these fish over big fish as it is delicious to eat.
- Due to low demand and supply in the market, its price is relatively higher than other fish.
Tangra fish brood rearing, artificial insemination and fry production:
The following methods are to be followed for brood rearing, artificial insemination and fry production techniques of tangra fish:
Pond selection and preparation
The brood rearing pond is 8-10 percent in size and 1.0 m deep.
Before releasing the brood fish, the pond is dried and at the rate of 1 kg per cent, 5 days after application of lime, 100 g of urea, 75 g of TSP and 4 kg of dung are used.
The brood rearing pond should be surrounded by a net.
Brown stock of tangra fish
From April to August of the year is recognized as the breeding season of the tangra fish. Before the breeding season i.e. in January-February, after collecting healthy strong and disease free tangra fish weighing 8-10 gms from the natural water body, 60-100 tangra per cent is stored in the prepared pond to make brood for artificial breeding.
Food application and care
For maturation of brood fish, twice a day, rice husk is applied at the rate of 25% fishmeal 30%, mustard oil 20%, meat and bone meal 25%. Food should be applied at the rate of 8-5% of the body weight of the fish. The growth of brood fish is monitored by pulling the net every 15 days from 2 months after stocking. Regular water quality such as temperature, pH, dissolved oxygen, ammonia and total alkalinity should be monitored.
Artificial insemination techniques
Mature males and females are transferred from brood rearing ponds to cisterns before the breeding season. Male and female fish are transferred to smooth Georgette Hapa in the ratio of 2: 1, respectively. Artificial springs are used to ensure oxygen in the cistern. Male and female tangerine are injected into the pituitary gland (PG) or ovaite solution under the thoracic fins.
Table 1: Artificial insemination of tangra fish with single dose of PG or ovoid hormone injection
The female lays tangra eggs 8-9 hours after the hormone injection. The eggs stick around the hopper in a sticky state. After laying the eggs, the broods have to be removed from the hapa.
20 to 22 hours after hatching, pollen is released from the eggs.
After the pollen ovary is absorbed, the pollen has to be fed. Renu pona is given boiled egg yolk solution 4 times a day for 6 hours. Arrangements were made to transfer the pollen pona to the nursery pond after keeping it in this condition for a week.
Tangra fish nursery management
Nursery pond selection and preparation
The size of the pond is 4-6 percent and the average depth is 1.0 m. For the preparation of the pond, the pond is dried and 1 kg of lime is given every century. Then 100 g urea, 75 g TSP and 6-7 kg dung manure are used. The pond should be surrounded with nylon net.
Fry collection and storage in nursery ponds
Hatchery-produced 7-day-old pollen fry can be stored at a rate of 8,000-12,000 per cent.
During storage in the nursery pond, the fry should be released after adapting well to the temperature of the pond water.
Apply food in nursery ponds
After storage in hatchery 7-day-old pollen fry nursery ponds, feed for every 10,000 fry.
Table 2: Level of food application in the nursery pond of Tangra fish
The pollen turns into finger pona 55-60 days after hatching, which is suitable for storage in farming ponds and survival rate is 55-60%.
Management and care
The growth of the body of the fish should be monitored by pulling the net every 15 days after 15 days of fry stocking. Regular water quality such as temperature, pH, dissolved oxygen, ammonia and total alkalinity should be determined.
Production and extraction of fry
After 55-60 days of stocking fry in the nursery pond, the pond is completely dry 5-6 cm. Sized tangra fish fry are available.
Following the strategy researched by the institute, it will be possible to ensure the availability of tangra fish fry in privately owned and government fish hatcheries. If the artificial breeding of tangra fish is expanded, it will be possible to increase the production of this species in this region and in the country through cultivation and it is expected that this species will pass from endangered status.