Mahseer is a potential aquaculture

Mahseer is distributed in India, Bangladesh, Nepal, Pakistan, Srilanka, Afghanistan, and Burma. It inhabits different rivers throughout the length & breadth of India.

Different species occupy different ecosystems ranging from tropical waters (35°C) to sub-Himalayan regions (6°C). Occur in streams hardly above sea level & 2000 m above sea level. T. putitora is commonly distributed at an altitude from 70-1891 m and Tor tor from 135-1891 m. Occurrence and distribution is controlled by water temperature. The seven species seen in India are:

• Tor putitora (Golden mahseer), Tor tor (Tor mahseer)

• Tor khudree (Deccan mahseer)

• Tor mussullah (Humpback mahseer)

• Tor kulkarnii (Dwarf mahseer)

• Tor progeneius (Assamese mahseer)

• Tor mosal (Copper mahseer).

HABITS:

Mahseer is a freshwater fish and it inhabits hill streams and fast flowing rivers. It is omnivorous, opportunistic feeder and feeds on green filamentous algae, aquatic insects, small fish, weeds and mollusks. Feed choice changes with age and size. Hatchlings have higher inclination towards planktonic food and fingerlings and growers prefer animal origin food. Mahseer migrate upstream, from the main river into the rivulets mainly during the southwest monsoon (July through September) for the purpose of spawning, this is when they ascend to substantial heights up to 2500 ft. Migration process is due to the reproductive biology of the fish and also in search of fresh feeding grounds.

SPAWNING:

Most of female mahseer mature above 390 mm in length and spawn from May to September. Breeding season of most mahseer species extends from July to September with a peak in July – August.

Most mahseer species are known to have very similar spawning behavior and breeding habits. Natural spawning habitats usually comprise the marginal lake areas. In addition to well-oxygenated water, water temperature from 21°C to 26°C proves to be effective for final maturation of eggs. The average fecundity is about 3100 eggs/kg body weight of the female. The fertilized eggs are demersal, lemon yellow or brownish golden in color and measure 2.8 to 3.2 mm in diameter.

GROWTH:

Hatching time depends upon the water temperature and takes 60-96 hours at 20-28°C and more than 96 hrs at temperatures less than 20°C. Reliable method to obtain fry and fingerlings is to grow mahseer juveniles in ponds and breed the adults using hormones. Intramuscular administration of ovaprim @ 0.20 ml/kg bw is given to the females.

Stripping is done 12 hours after administrating the second dose pituitary extract to female, the male requiring only one dose. For artificial fertilization, eggs are mixed with milt by dry method. Fertilization rate is 70-80% and hatching rate is 60-65%. The early hatchlings of mahseer are golden yellow and pass through a semi-quiescent stage during which they remain huddled in corners and crevices with their heads tucked away from light. In this condition, they are exposed to heavy predation. This lasts for about six days and forms the most critical period of its early life cycle. Mahseer growth response increase with increasing water temperature and it grows well in warmer place than in colder place. Mahseer can attain sizes upto 5.5 ft and weigh over 50 kgs.

USES:

Mahseer is a highly valued indigenous species. It is an outstanding game & food fish. As a sport fish, it provides unparalleled recreation to anglers from all over the world. It supports a substantial natural fishery in the major riverine ecosystems of India. Mahseer is a highly esteemed food fish & fetches high market price in north & northeast India. It is a potential species for aquaculture and there is an increasing interest for aquarium trade

CULTURE:

Mahseer is a potential aquaculture species. The old practice has been to rear wild mahseer in captivity. Brood fish grown in captivity can produce the required quantity of seed. Mahseer is suitable for both composite fish culture and monoculture. Hatchlings, fry, fingerlings and growers of mahseer accept pelleted feed and is capable of efficient utilization. Based on growth performance and feed utilization a 40% protein content in the feed is optimal. Mahseer grown on pelletized feed develops into excellent broodstock for induced breeding. Commercial culture is possible in warmer areas. In most cases, mahseer fry are raised to fingerlings and stocked in reservoirs and rivers.

Rearing of fry and fingerlings of mahseer were undertaken in cages in reservoirs. This would enable production of stocking material in reservoir without additional land space. In experimental cage culture carried out at Walwan reservoir, Mahseer stocked in nylon cages at a depth of 2 m. After 150 days of culture, average weight of Tor khudree was 35-106 g and that of Tor putitora was 15- 52 g. Survival rate was 98%. Cage culture with low-cost supplemental feeding is gaining popularity in the country.

Pen and cage culture can be extended to hilly rivers & creeks.

In properly managed ponds, an average weight of 175 g can be reached in 1 year.

Mahseer fingerlings can be reared on pelletized feed made of rice bran, groundnut cake and fishmeal (30:30:40).

Experiments conducted on the culture of khudree have indicated that mahseer fingerlings could be grown to 110-120 g in monocultures at a stocking density of 11000/ha in 8 months.