THOOTHUKUDI: The ICAR-Central Marine Fisheries Research Institute (CMFRI) has launched Integrated Multi-Trophic Aquaculture (IMTA) farming at Tsunami Nagar and Pullaveli along Thoothukudi coast. The project funded by the NABARD features the ICAR-CMFRI technology of IMTA cage, i.e., integration of fish with seaweeds and bivalves (mussels and oysters) for two years in a bid to double the income of fishermen.
CMRFI preferred fingerlings of Asian Sea Bass, which have high commercial value, being integrated with the filter feeder called green mussels and red seaweeds (Kappaphycus alvarezii).
The CMFRI scientists have categorised the project into two, one with IMTA farming at Kovalam beach near Tsunami colony, and the other with the non-IMTA farming method at Pullaveli coast, as the developments at both the places could give more insight at the end of the demonstration.
With the commercially viable and consumer-preferred Asian sea bass (koduva) grown in sea cages, the demonstration at Kovalam Beach involves the integration of red seaweeds (Kappaphycus alvarezii) and the filter feeder called green mussels. Whereas the non-IMTA demonstration at Pullaveli will have only Asian sea bass.
As per the IMTA technology of CMFRI, the cage with a diameter of six metres, made of HDPE pipes or galvanised iron for 2.5-metre depth, has inner and outer net compartments. The inner net is divided into two with the hapa net, for stocking fingerlings for up to two months. The outer net protects the fingerlings from predators. The sea cage is placed underwater at least 500 metres away from the shores, the scientists said.
Senior scientist Kalidas said that over 1,000 fingerlings of Asian sea bass (8 to 12 cm long) can be grown in one cage. At first, the fingerlings are left in the hapa net where it is fed manually with the pallet feed (artificial feed) for one or two months. The hapa net is removed after two months, leaving all the fingerlings in the inner net, he said. The scientist added that the fish are harvested at the end of the eighth month. Usually, October-June is said to be the potential period for IMTA practice, he added.
Meanwhile, the mussels (chippi) are typically placed on a rope surrounded by mesh to prevent them from parting. The rope is dropped between the inner and outer nets. As many as 16 ropes can be entrenched into the narrow space surrounding the sea cage. Another integration component of the IMTA technology is the cultivation of red seaweed on the bamboo rafts, close to the cage. Monoline method is followed to grow the seaweeds.
Explaining the food chain of IMTA methodology, scientist Kalidas said the excreta generated by the fingerlings, becomes feed for mussels and the seaweeds. "The excreta decomposes into organic and inorganic matter. The mussels feed on the phytoplanktons formed out of the organic matter. The red seaweed absorbs both organic and inorganic substances, and the uneaten feed given to the fingerlings," he said.
Dr PS Asha, principal scientist and scientist-in-charge of ICAR-TRS of CMFRI, said that the mussels yield 3-4 folds higher in a period of 30 days, while the red seaweeds show 4-6 folds increase, giving the fisherfolk an additional income. Moreover, at the end of the eight months, each sea bass fish grown in the cage will weigh 1.25 kg to 1.50 kg, which could fetch a minimum of `400 per kg, she added.
Sea bass is mostly exported to southeast Asian and other foreign countries. The IMTA technology will fetch a decent income for the fishermen's self-help groups, without affecting their business. The sea bass has been grown in sea cages at Chippikulam, Keezha Vaippar, Mottagopuram and Tespuram since 2015. However, this is the first time the cage is being integrated with other ocean species as a value addition.
Dr L Ranjith told TNIE that the IMTA is an efficient system that helps to control both organic and inorganic pollution in the natural open waters, thereby ensuring ecological balance. It is also an eco-friendly and sustainable option that provides a quick and steady income for the coastal fishers as an alternative livelihood option, he said. District Revenue Officer (DRO) C Ajay Srinivasan launched the IMTA farming Tsunami Nagar and Pullaveli in the presence of NABARD Chief General Manager R Shankar Narayan and CMFRI scientists.