Murrels or snakeheads belonging to the family Channidae (= Ophiocephalidae) are highly regarded food fish in the South and Southeast Asian countries. Their ability to breathe atmospheric oxygen makes it possible to keep them alive for long periods out of water and to sell them alive at high prices in the market. Besides the high-quality flavour and texture of their flesh, murrels are especially regarded as diet for invalids and recuperating patients. Though cultivated in many countries of Asia, murrel culture has not yet developed to major commercial importance.
There are over 30 species of murrels or snakeheads distributed in tropical Asia, including Northern China, and in Africa. Among these, the species of aquacultural importance are Channa (= Ophicephalus) striatus (fig. 24.3), C. marulius, C. punctatus, C. maculatus and C. micropeltes. Channa striatus, C. marulius and C. micropeltes grow to sizes of 1–1.2 m, whereas the other two species are smaller in size, reaching 22–30 cm. Though adult murrels of any size have a market in Asian countries, the preferred size is between 600 and 1000 g.
Murrels are very hardy and can tolerate unfavourable conditions. If kept moist, they can live out of water for long periods, and are known to survive droughts by aestivating for months in moist mud. The preferred temperature is in the range of 20–35°C, and the upper and lower lethal limits are reported to be 40 and 15°C respectively. Though sensitive to sudden changes in pH, they can survive in both acidic and alkaline waters. They are essentially fresh-water species, but can withstand low salinity brackish-water conditions.
The most common system of murrel culture is in earthen ponds ranging in size from 800 to 1600 m3 and in depth from about 0.5 to 2 m. Often the ponds have fine-meshed wire fencing to prevent escape of the fish. In Kampuchea and Vietnam, murrels are usually growth in cages moored near the shore or trailed behind fishermen’s boats. The cages vary in size from 40 to 625 m3. A traditional system of growing murrels in irrigation wells is practised on a small scale in India and neighbouring countries.
Being highly predacious and cannibalistic, murrels are generally raised in monoculture using, as far as possible, stock of the same size group. But in countries like Taiwan, murrels are stocked in carp and tilapia ponds to forage on unwanted fish. Recent experimental work in India shows the possibility of culturing C. marulius and C. striatus in swamp pondstogether with several species of local forage fish. Farmers in Thailand have in recent years started integrating murrel culture with pig and poultry production.