Hilsa, (Tenualosa ilisha), the popular migratory fish along with the Bengal river-sea ecosystems, is one of the delicacies of Bengalis, both at West Bengal and Bangladesh, associated with culture and emotions of Bengalis of the Indian subcontinent and even overseas. In spite of huge demand, production of Hilsa is limited to around 72000 metric tons, of which, India produces only 15-20%. The production of Hilsa is depleting due to over-exploitation and pollution in the ambient environment. According to the scientific reports, most of the Hilsa are captured before attainment of first maturity and do not get a chance to breed even once in the lifetime, and hence conservation and management of the stock need immediate attention. In this context, Indian Council of Agricultural Research (ICAR) has taken up a project entitled “Stock characterization, captive breeding, seed production and culture of Hilsa” involving CIFRI, CIBA, CIFA, CIFE, CMFRI, NBFGR and Visva Bharati University with financial support from National Agricultural Science Fund (NASF), on a network mode.
The ICAR-Central Institute of Brackishwater Aquaculture (CIBA), through its Kakdwip Research Centre (KRC) located in West Bengal, is playing a major role in standardization of protocol for the captive rearing of Hilsa in brackishwater ponds using formulated feeds by a team of CIBA scientists. When the collaborating institutes, viz., CIFRI, Barrackpore and CIFA, Kalyani Centre have taken up assessment of natural stock, habitat preference, biology of Hilsa in different ecosystems and standardization of captive breeding in freshwaters, under the CIBA component, development of formulated feed for Hilsa and experimental farm rearing of Hilsa in brackishwater ponds at KRC of CIBA has been attempted. Hilsa fry collected from Muriganga River through bag nets were transported to the pond side, KRC of CIBA Kakdwip, immediately in oxygenated polybags or aluminium handi fitted with aerators. Seeds were released in the pond after acclimatization at a stocking density of 8800 nos./ha. Pond water depth was maintained at 120-150 cm. Aeration was given to create water flow in the pond and to maintain desired oxygen concentration (>7 ppm). The live feed, such as copepods, rotifer and microalgae produced at KRC wet lab facility were supplemented in the rearing ponds. Also formulated feed was developed using the recently established experimental feed mill at KRC, and used for feeding the captive stock of Hilsa. Sampling was carried out monthly to observe the growth and health status of the fish. Hilsa fry of size (1.37 g, 52.97 mm) used for stocking, attained 330-423 g (320-350 mm) in 31 months with an estimated survival of 15-20%. The maturation process, with egg development up to stage III condition in female and sperm development in male, has been recorded in the pond reared Hilsa stock. Initially, the transportation of live Hilsa fry from the natural environment to pond and subsequent rearing process was a big challenge. With continued efforts of the scientists, it has now become possible to maintain live Hilsa in the pond for a long time and even in tanks using artificial feeds. This is a significant step towards the captive rearing of Hilsa. The CIBA scientists team are continuing their efforts for the development of Hilsa broodstock in brackishwater pond.
For the development of formulated feeds for captive Hilsa, the live feeds were gradually replaced by freeze-dried zooplankton powder and further gradually replaced by formulated floating pellets. In this trial, Hilsa fingerlings were completely weaned to floating pellets (protein 35 %, fat 12 %) within 45 days. Different wet lab trials were carried out in Recirculatory Aquaculture System (RAS) to find out protein and lipid requirement of Hilsa. The proximate composition, amino acid and fatty acid analysis of Hilsa body muscle of different growth stages have been carried out. Hilsa larvae produced through dry stripping from natural brooders were used for studying the first appearance of different digestive enzymes for the supplement of suitable feed items. Based on these observations formulated feed specific to Hilsa was developed.
Hilsa, known for its slow growth, the stock reared in the brackish water ponds at KRC of CIBA attained more than 400 g in two and half years time. This is the first successful rearing attempt of Hilsa in brackishwater pond in India by ICAR-CIBA, where the growth is 30% less than that recorded in nature. Dr K.K. Vijayan, Director, CIBA is optimistic that once the research efforts initiated by CIBA Kadwip Research Centre to produce Hilsa brooders in captivity will become successful, efforts on the captive breeding of Hilsa will be an achievable target in the coming years. This will open up a new horizon up in the ranching of young one of Hilsa into the Bengal waters and our goal of stock improvement and increased the production of Hilsa from the natural waters. Once the breeding and seed production technologies are standardized, a flagship programme could be taken up on Hilsa selective breeding for growth with technological backup from CIBA, which then may be used as an aquaculture species for culture in farmers’ ponds.
The scientist’s team comprises of Dr Debasis De, Dr T.K. Ghoshal, Dr Prem Kumar, Dr Shyne Anand, Dr G. Biswas, Dr Sanjoy Das and Ms Christina, L. from the Kakdwip Research Centre of CIBA, with technical support by Dr M. Kailasam from CIBA HQ, Chennai.