Air - Breathing Fish Culture

The culturable species of air breathing fishes are

1. Channa straitus - Big or Striped Murrel or Snake Head Fish
2. Channa punctatus - Spotted Murrel
3. Channa marulius - Giant Murrel
4. Clarias batrachus - Magur
5. Heteropneustes fossilis - Singhi
6. Anabas testudineus - Koi or Climbing Perch.

• Out of these, Channa striatus has highest demand in the market and is also commands a higher price.
• Next best are Clarias batrachus and Heteropneustes fossilis. The culture of the above species is profitable.

Culturable Areas

• The culture of air breathing fishes needs shallow waters with a depth of 50 - 75 cm.
• Ponds for air-breathing fish culture need not be fertilized by chemicals.
• Air breathing fishes may also be cultured in cages in running water systems like streams, canals and unmanageable waters like reservoirs.
• The air breathing fish culture is equally adaptable in waters unsuitable for conventional culturable species of carps as well as in carp culture ponds.
• Shallow ponds are useful for fishes, in which the fish has to spend less energy in travelling to surface for intake of atmospheric oxygen.

Seed Collection

• The seed of murrel, magur and singhi are collected from the natural resources, inspite of success achieved in induced breeding.
• Even today, seed collected from nature continues to be the most dependable source of material for stocking.
• Murrels attain maturity in two years are known to breed throughout the year.
• The fry of 2-4 cm can be collected all round the year and from rainfed ditches and shallow water bodies with abundant weeds. However peak spawning is known to occur just before the monsoon.
• The young ones emerging from the eggs move in shoals and their collection in large numbers is always easy. The fingerlings may not tend to move in shoals.
• Fry of giant murrel can be identified by their dark grey body and a lateral orange yellow band from eye to the caudal fin.
• Fry of stripped murrel have bright red body with reddish golden band and a dark black band from eye to the caudal fin.
• The spotted murrel fry can be recognised by their dark brown body with a golden yellow lateral band and a mid dorsal yellow line on the back.
• In murrel culture, it is better to stock fingerlings rather than the fry. Cannibalism is found in murrel fry.
• The survival rate of fry which produced by induced breeding will be poor and to maintain the spawn and grow them to the fry stage is difficult.
• The spawn do not eat anything for two days after their emergence from eggs. Hence, the fry should be trained to accept supplementary food in separate ponds.
• The supplementary feed consists of boiled eggs, silkworm pupae, minced trash fish and worms along with yeast and vitamin B. It is given for about 15 days at the rate of 20 % of their total body weight.
• The fry reach the fingerling stage of 4-6 cm length within a month. The cat fishes breed twice in a year with the peak breeding season during rainy season.
• Magur fingerlings can be identified with their longer dorsal fin and slate colour. Singhi fingerlings are having a short dorsal fin and pink colour. Koi fingerlings can be identified by the dark spot on the caudal peduncle and greenish hue on the dorsal surface of the body.
• The magurs make a hole of 25 cm depth in the bund below the water surface.
• The fertilised eggs adhere to grass and are guarded by the males. 2,000 - 15,000 fry can be collected from each hole with the help of small fine meshed hand nets and reared in nurseries until they reach fingerling stage with about 5 cm in length.
• Magur can be cultured in ponds for the production of fry.
• At the centre of each compartment, a hole of 30 cm diameter is dug and is provided with few aquatic plants.
• After releasing both the sexes, about 5,000 fry can be collected from each compartment within 10 days.
• The males and females can also be reared in small earthern ponds. They can be stocked 20,000 / pond and fed either with filtered zooplankton or chopped fish meal and ground nut oil cake.
• The fry can be reared for 15 days in nurseries.
• The peak season for the collection of seed of singhi is pre-winter period when paddy is harvested and the low lying fields get exposed.

Seed Transport

• The fry or fingerlings of air breathing fishes can be transported without oxygen packing.
• Polythene drums or iron drums are used for transport of fry or fingerlings.
• The carrier must have enough space for their habitual surfacing to breath atmospheric air.
• The carrier should have a small amount of aquatic weeds like Vallisneria, Hydrilla,  Myriophyllum and Ceratophyllum.
• The weeds may help to avoid jumping of the fish during transportation. If the distance is more, it is better to transport them in oxygen packed polythene containers.

Pond Management

• Nurseries are about 10 - 15 m² having a water column of 50 cm.
• These are stocked with 0.2 - 1.5 million fry / ha.
• Prior to stocking, manuring is done with raw cattle dung at the rate of 500 Kg / ha alone.
• The soap - oil emulsion to eradicate insects is applied to the nursery water.
• Fry and fingerlings of magur and singhi collected from natural resources require nursery management. But, murrels have to be trained in nursery ponds before stocking.
• After nursery management the fingerlings are to be transferred in stocking ponds.

Stocking

• Uniform sized fingerlings are chosen for stocking.
• The fingerlings are disinfected with 2 % KMNO₄ solution for 5 minutes or dipped in 200 ppm formalin solution for 50 seconds before stocking.
• Wounded fingerlings are treated with 0.3 % acriflavine for 5 minutes.  These fishes may escape through climbing or burrowing.
• The pond bunds should be firm with heavy log or wood or fenced with bamboo cane or wire screens to a height of about 50 cm.
• More fingerlings can be stocked in their culture system. 40,000- 60,000 fingerlings / ha of cat fishes can be stocked in monoculture systems.
• In polyculture systems 20,000 - 30,000 fingerlings / ha of cat fishes may be stocked.
• In monoculture systems, 15,000 fingerlings / ha of giant murrels, 20,000 / ha in case of striped murrel and 20,000 - 30,000 / ha in case of spotted murrel are stocked.
• In polyculture systems, striped and spotted murrel may be stocked at a rate of 20,000 fingerlings / ha in the ratio of 1:1. Polyculture of murrels - carps and catfishes - carps is also possible with proper care and management.
• The seed of air breathing fish should be stocked only when the carps have grown to a minimum of 300 gram, so that air breathing fishes may not prey on the carps.
• With this, not only an additional income can be obtained through the yield of air breathing fish, but also the growth of carps can be enhanced.
• The later is possible, as the trash fishes which may compete with carps for food and space are eradicated by the growing air breathers.

Feeding

• To maintain an abundant food supply for growing air breathers, the stocking pond must be rich in animal food source like frog tadpoles and trash fish.
• If this food source is not sufficient tilapia may also be grown in murrel and cat fish ponds.
• Dried marine trash fish also used in fish culture and is more economical.
• Feeding can be given to catfishes with fish offal or slaughter house waste, dried silkworm pupae mixed with rice bran and oil cake in the ratio of 1: 1: 1: 1.
• A mixture of oil cake, rice bran and bio-gas slurry in the ratio of 1: 1: 1 has provided successful low cost feed for singhi.
• Rice bran and poultry feed in 3 : 1 and biogas slurry and rice bran in 1 : 2 also be given at the rate of 5 – 8 % of body weight.
• During the eight months semi-intensive culture in stagnant ponds, the air - breathing catfish stocked may be fed at the following rate daily during dark hours of the day to obtain better feed utilisation.

The feed and its ratio in different months in cat fish culture.

Period	weight of feed Kg / day (stocking density 50,000 / ha)	feed ratio trash fish : rice bran
1-2 month	12	1 : 2
3-4 month	24	3 : 1
5-6 month	35	1.5 : 3
7-8 month	48	1 : 3

 

• The feed may either be broadcast in the pond in small amounts from the bund or may be served in feed baskets lowered near the bank in addition to broadcasting of feed to ensure availability of feed to all the fishes in the pond.
• Light traps can be installed in murrel ponds, by which the insects may be attracted by light and utilised by murrels as a protein rich food.
• Trained murrel fingerlings will also accept cheap dried marine trash fish soaked in water, Slaughter house waste and silkworm pupae as a source animal protein can also be used.

The feed for murrels in different months

Period	Feed Kg / day (stocking density 50,000 / ha)
1-2 months	3.75
3-6 months	11.25
5-6 months	17.50
7-8 months	25.00

Growth and Production

• If the management practices are proper, giant and striped murrels can attain a growth of 1-2 Kg / yr and 0.75 Kg / yr respectively, whereas spotted murrels grow to 160 grams in 8 months.
• Cat fishes are known to grow slowly when compare to murrels. Magur and singhi grow to 0.2 Kg and 0.1 Kg respectively. The conversion rate with recommended feed is approximately 2:1.
• Murrels with forage fish as supplementary food yield about 4 tonnes / ha / yr.
• Magur with dried trash fish and rice bran supplementary feed, give the production of 10 tonnes / ha / yr.  Singhi gives a yield of 4.4 / tons / ha / yr.
• Polyculture of murrel and koi, fed with rice bran, mustared oil cake and trash fish, gives a production of 11.8 tons / ha / yr, while magur and singhi fed with rice bran and trash fish give an yield of 5 tons/ha/yr.
• Mixed culture of 3 species of murrels produce 4 tonnes / ha / yr when fed with soaked and dried marine trash fish and fresh silkworms pupae as food. In the intensive culture magur can give 7 tonnes / ha / 5 months.

Culture with Carps

• With a stocking density of 5000 / ha of Indian and Chinese carps and 1,000 magur fingerlings produce 2,518 Kg / ha / yr of carps and 3,711 Kg / ha / yr of magur.
• This indicates that the polyculture is more profitable and it is useful to include magur in the carp culture system.
• With a stocking density of 20,000 / ha of magur along with left over carps (after partial harvesting of carps) production of 3.96 tonnes / ha / yr is obtained with 50: 30: 17: 3 ratios of rice bran, fish meal, groundnut oil cake and minerals as supplementary feed.
• The magur is found suitable for composite fish culture of carps in place of common carp.
• Magur, koi and singhi are also suitable to culture along with a highly priced carp makhana.

Harvesting

• Summer season is ideal for harvesting air - breathing fishes from ponds.
• The pond is drained and the fishes are harvested with the help of scoop nets or hand nets.
• Due to their high demand and market price, the culture of this air - breathers provide profitable income to fish farmers with simple management techniques.

Cage Culture

• The air - breathers can be cultured in cages also. The cages are prepared with mats made up of split bamboo in running waters.
• The optimal cage area measures 2m X 1m X 1m in size. The top of the cage is half covered with mat and the uncovered part is covered with a net to facilitate feeding and to prevent escape of fishes.
• Synthetic fibre mesh is also used to prepare cages.
• Magur are stocked at a rate of 200 / cage, fed with 10% of body weight on dried trash fish, oil cake and rice bran and produce 10 – 12 Kg / m³ / yr.
• Singhi produces 12-20 Kg / m³ / yr with a stocking density of 100 - 150 / cage and 10 % of body weight feed of silkworm pupae, rice bran and mustard oil cake.
• Koi produce 4.2 Kg / m³ / yr with a stocking rate of 50 - 100 /cage with the same food as singhi.
• Spotted murrel produce 4 Kg / m³ / yr with trash fish and rice bran.
• The air breathing fish culture is highly profitable, as well as a rich source of animal protein. This fish is considered as a delicacy, and commands a very high price and continuous demand in the markets.