Culture of Murrel

Species profile

Murrel belongs to Channidae family. They are widely distributed in tropical Africa (three species) and Southern Asia predominantly in India, Pakistan, Afghanistan, Nepal, Sri Lanka, Thailand and China. A total of 33 species are globally identified, of this 30 belong to Channa genera, and remaining 3 belong to Parachanna genera. Only 13 species are stated in India.

Murrel is also called as snakehead as it looks like a snake. Murrel is valued and fetches a higher market price especially in states like Andhra Pradesh, Karnataka, Tamil Nadu, West Bengal, Assam, Uttar Pradesh and Haryana due to its eminent nutrition and medicinal value. Hardy nature and ability withstand longer time out of water add greater value to Murrels in the market. Specialized trade involving live fishes is also practiced in India.

Murrel is one of the indigenous air breathing fish; there is a suprabranchial accessory respiratory organ in the murrel head. Murrels can even survive in lower dissolved oxygen levels.

The most important aquaculture species of murrel in India is the striped murrel (Channa striata), the great snakehead murrel (Channa marulius) and the spotted snakehead (Channa punctata). The culture technology is standardised only for striped murrel.

Broodstock

The brood fish are reared in earthen and cement cistern. Smaller size pond (0.04 to 0.1 ha) is favoured rather than larger size pond due to its easy management. The suggested pond depth is 1.0 – 1.5 m. Pond dyke should be made strong enough to prevent fish escape during the rainy season. The earthen pond is prepared similar to that of ponds used for culture of the Indian major carp. The manure (5000 kg/ha/ yr) and the liming (300 kg/ha/yr.) are applied to produce the natural fish food organisms. A total of 2000 to 2500 kg/ha is stocked and are fed with low market value fish and rice bran at the rate of 2 – 3 percent of body weight.

Typically, two year old striped murrels are used for breeding. A 100g female is expected to deliver an average 6000 eggs. The small fish is easy to handle rather than larger size fish. Inbreeding depression occurs due to the use of same blood brood fish and it can be avoided through introduction of brood fishes from outside source (including rivers, stream, other farmers)  every year. To adapt to the captive condition, the new brood fish can also be reared in brood tank.

The size of pond and the stocking density depends on the size of fish and targeted growth of fish. The supplementary feed is essential at daily two rations at the rate of 3 – 4 percent of body weight when the stocking density is higher. Adding aquatic weeds in about 20% of water area stimulate the natural environment. Regular examination of maturity, proper care to brooders, implant hormone pellets and post-operative care etc need to be taken care of. Total replacement of water has to be done at least once in a week at regular interval to maintain the water quality.

The sexes are distinguished by using secondary sexual characteristics during the spawning season. The female fish develops a bulging soft abdomen due to the development of ovary and the genital pore becomes reddish and oval shape. The head of the male is round shape and has the smaller genital papilla.

Breeding

In striped murrel, the spontaneous and induced breeding are practiced.

Natural breeding

Fish seed in natural spawning is produced by providing a natural environment through the use of aquatic weeds. The brood fish’s size of 100 – 250 g are stocked in a shallow water depth small size pond. The synchronized movement of brood fishes occurs after the month of March. They build a nest with the use of aquatic weed and lay eggs in the shallow water area of the pond. The eggs are collected from the pond and are reared in the hatchery. This breeding method has a poor breeding response ie. about 20 – 30 percent.

Induced breeding

The breeding occurs twice in a year (southwest and northeast monsoon), exclusively in the rainy season. A water depth of 40 – 80 cm is preferred for spawning tank. The aquatic weed (water hyacinth) should cover one-fifth of the breeding pool, which stimulate the spawning. The recommended temperature for spawning is about 25 to 28^oC. The requisite administered dose of HCG is about 2000 IU/kg of body weight for the female and for male 1500 IU/kg of body weight. A poor breeding response is observed when HGC is used when compared to the extract of carp pituitary. The desired dose of carp pituitary extract is 20 – 30 mg/kg and 30 – 40 mg/kg of body weight for male and female fish respectively. The injection is given by intramuscular method (at the base of pectoral fin).

Fishes have unusual spawning characters and chasing occurs. The spawning usually takes 16 – 18 hrs. A 1 kg female fish releases about 10000 – 15000 eggs. The eggs are free floating, spherical, non-adhesive and bright yellow colour. The fertilized eggs are transparent and unfertilized eggs are opaque. Fertilized egg size diameter ranges from 1.2 – 1.5 mm. The fertilized eggs are collected by using the plankton net and is shifted to the FRP container for hatching. Hatching time takes between 20 – 24 hrs. The fertilization rate is about 80 – 98 percent and the average hatchling rate is 70 – 90 percent. The newly hatched larvae size range between 3.0 – 3.5 mm. Also, an improved rate of fertilization and hatch rate is noticed in carp pituitary extract than the HCG.

Fry production

After hatchling at 0 hrs the digestive tract appears as a straight tube lying to the yolk sac, but with no accessory digestive organs (liver, pancreas and gall bladder). The yolk sac absorption is very fast after 1 – 2 days of hatching and the digestive tract is developed. After three days, fry starts to consume the feed such as zooplankton (protozoans, rotifers, and cladocerans). This is continued until they grow to the size of 20 – 30 mm. The expected survival rate is about 50 – 60 percent at 20 – 25 days.

Heterogeneity and cannibalism are the two phenomena, which affect the growth and survival of the fry of striped murrel in large numbers. The heterogeneity occurs due to improper distribution of food, higher stocking and less space for individual fry. The cannibalism directly enhances the heterogeneity and it is avoided through optimum stocking and high feeding rate. Typically, 2 – 3 percent of fry turn into shoot fry, which leads to increased small size fry. It can be removed through periodic segregation (weekly) of bigger size fry. Initially, the idealist weaning feed quantity is 8 – 10 percent body weight of fish or until satisfaction, which curtails the cannibalism. The artificial feeds are offered after full development of digestive tract, with the protein amount of 40 – 50%. Finely chopped low market value fish are fed to the fry. The feeding rate is tweaked according to the intake amount and feeding behaviour of fish, which helps to enhance the survival rate.

Fingerlings production

The fingerlings consume the zooplankton and small crustaceans (especially insect). The live feed such as tubifex and earthworm are good food for hatchery rearing fingerling.

Striped murrel are stocked with higher density, owing to the presence of additional air breathing organ. A reduction in fish growth is observed when it is more than the optimum stocking density. Studies have attempted to establish standard stocking density of striped murrel, but the stocking rate is extremely variable ranging from 20000 to 460000 ha/yr. A greater survival of 76.67 percent has been recorded with a stocking density of 15000/ ha. Another study assessed the effect of stocking density; a better growth rate was registered with a stocking density of 50 m² than those of the 100 and 150m². Higher stocking is taken up farmers due to unscientific belief. Farmers stock higher stocking density, since they anticipate higher mortality and thereby hope that the higher number of fry will cover and compensate the higher rate of mortality. The higher stocking leads to wastage of resources and increases the cost of operation.

The fishes are fed by combination of both low market value fish and rice bran with a ratio of 3:1 to 8:1. This also highly varies due to fish availability in the local market and market value of the fish at a given time. However, the fishes have to be practiced to take floating feed rather than low market value fish, to reduce the operating cost. Fishes are fed at 6 – 8 percent of the body of the fish. If cannibalism still continues, it is advised to increase the feeding quantity to ensure higher survival. The protein requirement of fingerlings of striped murrel is about 40 – 45 percent. The anticipated survival is 30 – 40 percent.

Grow out production

The pond size of 0.1 – 0.2 ha is ideal for grow-out of striped murrel, with a water depth of 1 to 1.5 m. The dyke should be steep to prevent the fish escape from the ponds. Fishes reach the surface water due to lack of sufficient oxygen, which increase the energy loss resulting in mediocre growth.

Aquatic weeds are good for striped murrel, which provides the shadow in sunny season, provide the protection against poachers and encourage the insects growth. Fish is likely to consume the aquatic insects. For grow out, the recommended stocking size is more than 10 g. Covering the ponds by the net prevents the entry of birds and thieves. The stocking density of striped murrel is about 10000/ha, at the feeding rate of 5 percent of the body. The stocking density of fish directly alter the growth of the fish, thereby stocking density is decided based on the stocking size of fish and targeted fish growth. The expected growth is 600 – 800 g in a year, fish production ranges between 2.0 – 2.5 tons/ha/yr.

References

1. Bugar, H., Wulandari, L. and Harteman, E., 2017. Snakehead Fish (Channa Striata): Semi-Induced Breeding and Larval Growth. Indian Journal of Science and Technology, 10(11).
2. CIFA, 2016. Training programme on seed production of Anabas, Magur and Murrel. Central Institute of Freshwater Aquaculture, Bhubaneswar, India
3. Laxmappa, B.,and Vijay Babu, V.  2014. Present status and prospects of Murrels Farming in Andhra Pradesh, India. International Journal of Fisheries and Aquatic Studies. 1(5): 22-31
4. Muthmainnah, D. 2013. Growout of Striped Snakehead (Channa Striata) in Swamp Water System Using Fences and Cages,   4th International Conference on Biology, Environment and Chemistry, Singapore
5. Rahman AM., Arshad, A., Amin S.M.N. and Shamsudin, MN. 2012. Growth and survival of fingerlings of Threatend snakehead, channa striata. Asian journal of animal and veterinary advances.
6. Wee, K.L. snakehead (channa striatus) farming in Thailand, FAO.