Chennai
Pond culture and cage farming techniques in the sea have been popular means to counter the diminishing fish catch in our natural waterbodies. However, the huge potential provided by brackishwater wasn’t explored due to a lack of suitable technology.
ICAR-Central Institute of Brackishwater Aquaculture (CIBA) successfully harvested and demonstrated its first-of-its-kind three-tier cage farming technology, used to cultivate sea bass, roping in the local community to provide an alternative livelihood for the fishermen.
The pristine backwaters in Vennangupatti village was selected as a potential site for its good water quality and it was sheltered from intense wave action. CIBA teamed up with National Institute of Ocean Technology (NIOT) to manufacture the cages used to cultivate sea bass, a profitably viable species. While cage farming in the sea is popular, this is the first time the technology has been transferred to the brackish water using the three-tier model.
Dr M Kumaran, Principal Scientist, CIBA, explained, “During Phase 1 (nursery), fish fry of 1 cm length in fixed net hapas is reared for 45 to 60 days until they are 5-6g in size. We also provide indigenous feed called Seebass Plus, which is used 8-10% of the body mass during this stage. For example, for 1 kg of biomass, 800g of feed is administered per day, in two sessions. Since it is a carnivorous fish showing cannibalism tendencies, the fish are segregated based on size during this stage once in 5 days. In Phase 2 (pre-grow out), the nursery reared fingerlings are moved to a circular pre-grow out cage, for three months, until it grows to 90-100g in size. In Phase 3 (grow out), the juvenile fish are transferred to a bigger grow out cage at a density of 15-20 kg/m3 for 5-6 months, until they grow to a size of 750g and above. The fish can be partially harvested for easy marketability.”
The cage was designed, keeping in mind the conditions of the creek, said Dr R Kirubagaran, Scientist, NIOT. He added, “We studied the properties such as salinity and pH qualities of the water, wave height and speed, water movement and then came up with the design. The cages are designed using high-density polyethylene (HDPE), where these pipes are filled with polyurethane foam, to make it float. These tubes are joined using brackets to form a cage and have nets tied to it. These cages can last for approximately six years.”
This initiative has been received favourably by the local community as other villages around Vennangupatti and Puducherry expressed interest in replicating this technology. Dr KK Vijayan, Director, CIBA, said, “The technology can be replicated. We have trained the youngsters in Vennangupatti to not only cultivate the fish but also make the cage. This is a part of Attracting and Retaining Youth in Agriculture (ARYA) initiative and they could be the ambassadors, sharing the knowhow with other villages. The fisher folk depending on the brackish water for their livelihood could fish only during monsoon and post-monsoon seasons. With this technology, the local communities can become self-sufficient and take the initiative to scale up.”
Saran A, a local fisherman and Secretary of APJ Abdul Kalam Fish Producers Self-Help, said that after the success of the first harvest, they hope to scale up soon. “We started this as a team of 10 people. Now, each of us wants to have our own cage,” he concluded.
Economics of sea bass cultivation
CIBA teamed up with the local fisher folk, who have the traditional use of the creek, to cultivate the sea bass, which will be sold to the Tamil Nadu Fisheries Development Corporation Limited (TNFDC), for approximately Rs 400/kg. Dr Kumaran explained the economics, “The entire production cost (minus the cage), including the seed, feed, labour and transportation of feed works out to Rs 190-200 (approximately) per kg of sea bass, which is sold for Rs 400/kg, assuring alternate livelihood for the local fishermen.”
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