WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2015 47 (CONTINUED ON PAGE 48) Catfish. There are two catfish groups, smaller catfish Heteropneustes fossilis (singhi) and Clarias batrachus (magur) and larger catfish Wallago attu, Pangasius pangasius and Aorichthys aor. Both groups are suitable for cage culture because of their good growth and high market demand. Because of insufficient breeding protocols and nonavailability of commercial seed, the cage culture for minor carps has not yet developed. Minor carps (Labeo bata, Labeo calbasu, Labeo fimbritus, Labeo gonius, Labeo kontius, Cirrhinus reba, Cirrhinus cirrhosa, Puntius sarana) have high market demand locally. The major disadvantages associated with minor carps are that consumer preference is regionally specific, they are not voracious eaters and their growth is slow. The growth and yield characteristics, design and structure requirements of cage production , development of optimum stocking and health management protocols and proper feed for cage culture have not been studied in detail and further research is needed to demonstrate the suitability and economic viabilities of these species for cage culture. Cage Culture of Sutchi Catfish The sutchi catfish Pangasianodon hypophthalamus (also known as the striped catfish) is fast-growing, highly popular as a foodfish and a valuable species in Asian aquaculture. Originally known as Pangasius sutchii, the native range of this riverine freshwater species is limited to the Mekong River. Sutchi catfish are omnivorous, feeding on algae, higher plants, zooplankton and insects, while larger fish also take fruit, crustaceans and fish (Rahman et al. 2006). The fish is extensively cultured on commercial fish farms in Thailand, Vietnam, India, and Myanmar. It became a major candidate species for freshwater cage culture in India because of its fast growth, well-developed culture systems, omnivorous feeding habit, high acceptability of artificial diets, tolerance of high stocking densities, improved disease resistance capacity and tolerance of a wide range of environmental parameters. Sutchi catfish are cultured in large floating cages in reservoirs (Fig. 1) or stocked into earthen ponds. Fish are fed a prepared diet and can reach harvest size of around 1.5 kg in 8 months. Fingerlings weighing from 50-100 g are stocked into cages at 5-10 kg/m3. Yields from cages average around 80 kg/m3/ yr but up to 170 kg/m3 has been reported but the growth and yield characteristics of this fish in cages have not been studied in detail. Problems and Prospects of Sutchi Catfish Cage Culture Flesh quality is the most important factor determining the consumer preference and price of the marketed fish. Farmed sutchi catfish from India fetches low prices in the domestic market and moreover, it is less preferred in the international export market because of its poor flesh quality. In some parts of the country, yellow discoloration in the belly portion of sutchi catfish has been observed, reducing the market demand and consumer preference. This undesirable yellow color in fish may be attributed to high lipid content of the diet, poor water quality and other environmental factors, and the level of corn in the feed. Flesh quality can be improved to a large extent by judicious choice of feed ingredients/ supplements. Modifying the protein to energy ratio is another approach, inasmuch as low protein feed has been shown to reduce fat content and increase the shelf life of the meat. Intensification of fish production through cage culture of Pangasius will demand the creation of a new value chain system, FIGURE 1. Cage culture of sutchi catfish in Indian reservoirs.
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