Catfishes belong to four families; namely, the Ictaluridae, Claridae, Pangasidae and Siluridae and are widely distributed around the world. The traditional culture of catfishes have been practiced in Southeast and South Asia. Catfishes are considered high value species in certain areas whereas in other areas are considered lower and medium value market species. Catfishes are hardy in nature; they have the ability to stand longer time without water and have an accessory respiratory organ. There is a specialized trade of live fish in some places of Eastern India.
The most important aquaculture species of Catfish is the Asian catfish, Clarias batrachus. It belongs to Claridae family. Another important species is the Clarias macrocephalus which is highly preferred due to its appearance and flesh quality. However, because of unavailability of seeds and poor growth performance, it has attracted least attention.
Clarias species are normally found in freshwater and brackish water with lower dissolved oxygen. They have the ability to grow even in poor environmental condition. They are reared up to market size in earthen ponds, whereas, in Eastern India, it is grown in partially improved swamps. Clarias batrachus normally called as magur in India has greater value and high demand in India due to its therapeutic value.
A small cement cistern size of 10 – 20m2 is recommended for better management. The bottom of the tank is to be filled with about 2 – 3 cm soil and the water level is to be 0.25 to 0.30 m. The fertilizer (100g single super phosphate and 2 kg cow dung) are provided for nourishment of plankton growth. The tanks have to be prepared about a week before stocking of fry.
A newly hatched larva consumes the yolk sac up to 3 dph (days of post-hatchling). After yolk sac absorption, the larvae are fed with mixed zooplankton such as the copepods, daphnia, artemia, tubifex, custard egg, etc. After 8 days the larvae are fed with starter M (a product of CIFA) to obtain better survival and growth.
The recommended stocking density is about 1000 – 1500/m2. Regular cleaning of uneaten feed and debris, adequate supply of aeration, and water management have to be taken care. It is advised to replenish 50 – 60 percent of water twice daily. Aerial respiration commences after 10 – 11 days. Larvae growth measures about 10 – 20 mm length, 30 – 40 mg weight during 15 – 20 days of rearing.
The better growth and survival are obtained with fry stocking size of 1 g (40 – 45 days) with a density of 50 – 100 m2 in fingerling production. Feeding has to be adjusted according to the weight of the fish couple of times in a month. The fry is fed twice a day at 6 – 8 percent of body weight with 30 – 32 percent of protein. Shooting behaviour is normally found at this stage. To avoid this, the larger sized fishes have to be segregated at regular interval to get the enhanced survival rate. It reaches about 4 – 5 g during 60 – 70 days.
For grow out of C. batrachus, small ponds of size 0.02 – 0.1 ha is preferred. The water depth is to be maintained at 0.50 – 1.0 m. The pond should have a suitable slope of 1:2 – 1:3, and height of the dyke should be above 100 cm from the water level. C. batrachus moves from one pond to another pond especially during the rainy season. So, the pond has to be constructed in such a way to prevent this migration. The pond is prepared similar to carp grow out pond. The unwanted or predatory fishes and their eggs are eradicated by using the mahua oil cake @ 2500kg/ha/m or bleaching power @ 350 kg/ha. The agricultural lime @ 200 – 250 kg is added when the soil pH is above 6.
Commercially, most of the farmers stock about 200 fingerlings/m2, although the recommended stocking density rate is less than half of it (50 – 70/m2).
An improved growth and survival is obtained with a size of 3 – 5 g of C. batrachus. Feeding is adjusted according to the weight of the fish twice in a month. Fishmeal based compound feed with 30 – 32 percent is preferred for C. batrachus. The fingerlings are fed two rations at 3 – 5 percent of body weight. It attains marketable size about 100 to 150g in 10 – 12 months. Harvest is done by hand picking method after complete dewatering of the pond. An average production is 2 – 3 tons/ha in 10 – 12 months.
Mortality due to the bacterial and fungal pathogens are often associated with environmental stress. The CIFAX, potassium permanganate and Oxytetracycline (OTC) are used to manage the infections.
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