Production of Malabar Labeo

The Malabar labeo, Labeo dussumieri is a fresh water fish endemic to southern India and Sri Lanka, found in west flowing rivers of the Western Ghats up to north Canara. It inhabits the flood plain areas, reservoirs and backwaters. Its maximum size reported is 50 cm length and 2 kg weight. In Kerala, the species is one of the esteemed food fish and commands a higher price as compared to the major carps.

The Malabar labeo is herbivores and illiophagic. It is benthic in nature, which feeds by browsing at the bottom and main food items include detritus, decaying organic matter, diatom, green algae and submerged aquatic vegetation. In summer season, the fish is found to thrive in the deeper waters in the upstream reaches of river systems. It migrates massively for breeding during monsoon- a phenomenon vemacularly known as 'Thooliyilakkam' in Kerala.

Body of the fish is elongated and compressed with snout slightly projecting beyond mouth, without any lateral lobe. The mouth of the fish is sub-inferior with fleshy and fringed lips; with two-minute pairs of rostral and maxillary barbels. The width of the head equals its length behind the angle of the mouth. Numerous pores are present on the snout, which extends posteriorly as far as the orbits and below the nostrils. The dorsal fin with concave upper edge commences midway between the end of the snout and ends at the base of the anal fin. Caudal fin of the fish is deeply forked. The colour of the body is greyish; scales small and having a reddish centre, edged with a darker side.

The breeding protocol for Malabar labeo has been developed by ICAR-NBFGR with Regional Agricultural Research Station, Kumarakom. Due to the concentrated effort to revive this species, the fish received an IUCN status upgradation from “endangered category” to “least concern” category, as assessed in the Conservation Assessment and Management Plan (CAMP) workshop (1998).

Seed Production

Broodstock management

The broodstock can be collected from the flooded rivulets using trap made up of bamboo during the onset of monsoon, their breeding season. The broodstock is raised in earthen pond having a minimum water depth of 1.5 m at a stocking density of 2000 kg/ha. Periodic manuring is done with cow dung @ 250-1000 kg/ha fortnightly to facilitate plankton production. The fish is fed daily at 2% of the body weight with a formulated diet having 30-35% protein comprising of rice bran and groundnut oil cake or a commercial feed. Periodic water exchange in pond at definite intervals stimulates gonadal development.

Selection of brooder

Sexual dimorphism is very similar to Indian major carps and is exhibited only during the breeding season. The female can be identified by distended and swollen abdomen, and eggs will ooze out with slight pressure. The vent appears reddish and vascular. Male have a streamlined body, extruding milt on slight pressure. The pectoral fins of the male become rough during breeding season and are smooth in case of the female.

The ovary is bilobed and slightly asymmetrical. The mature ovary is dark green in colour and is highly vascularised. The testis is pale white and bilobed. Presence of a distinct and a single mode of mature ova and only one clutch of mature oocytes in the ripe ovary indicate short total synchronous spawning habit of fish. The mature eggs are greenish and spherical with a diameter of 1.0-1.3 mm. The fish is found to attain maturity by the end of the first year at a size of 25cm for female and 23.5 cm for male. The fecundity is 15,000- 25,000/kg body weight.

Spawning

Malabar labeo spawns once in a year, and peak breeding coincides with monsoon. Induced breeding can be attained using synthetic hormones like Wova FH @ 0.3 ml/kg for female and @ 0.2 ml/kg for male, in a single dose. Spawning can be facilitated in circular breeding pool by providing circular and concentric water flow. Sympathetic breeding is possible by stocking together several sets of brooders and hormonal administration of 50-60% of the broodstock under Chinese hatchery system. Spawning takes place in 9-10 hours after exhibiting vigorous courtship behavior. Fertilisation rate ranges from 64-100%. The fertilised eggs are spherical, translucent, demersal and non- adhesive.

Incubation

The fertilised eggs are transferred to circular incubation pool of the Chinese hatchery system and hatching takes place within 10-12 hours, with concentric flow of water @ 6-8 1/s as compared to 20-22 hours in the hapa system. Hatching rate ranges from 80-100%. Hatching of eggs is also performed in floating egg trays with flow-through system in which the incubation period is 17-18 hours. Hatchlings are transparent and free swimming with yolk sacs; yolk gets absorbed within 1-2 days.

Rearing of hatchling

The hatchlings are transferred to nursery hapa installed in earthen nursery pond or cement tank. The preparation of nursery pond and other management aspects are similar to that explained for the major carps.

Rearing of fry

After a week, the hatchlings are released to previously prepared earthen pond. Fry are raised mainly on plankton and supplementary feeding is done using rice bran, groundnut oil cake or powdered commercial pellets @ 3-5% of the body weight. The preparation of nursery pond and other management aspects are same as that explained for the major carps. The fry attains 7-8 cm in three months and are easily collected by fingerling net.

Pond Farming

The farming practices of Malabar labeo are similar to that of Indian major carps and it is a good species to replace mrigal in composite culture of carps. In earthen pond, the fish grows 650-1200 g in a year with supplementary feeding. Under cage culture systems, the fish attains 600-700g in 8 months.

Source : Department of Fisheries, Government of Kerala