A Poseidon adventure

Dr SK Ghosh accentuates the importance of mariculture, details the various fish farming systems and discusses the various problems in the Indian context

Mariculture is a very recent development in the fisheries sector in which the farming of selected varieties of fish is done on the shore or in coastal waters. Farming is also practiced in the marine waters off the coast in cages or rafts anchored in suitable places. Japan, Australia, Norway, America and many other countries are adopting these activities and utilising their coastal waters.

1 Mussel culture activity 2 Pearl culture project at Mandapam 3 Seaweed farming in Palk Bay

However, in India the mariculture activity at present is limited to the onshore farming of mud crabs and offshore farming of mussels, clams and edible oysters, mainly in Kerala, West Bengal and Orissa.

The mariculture production in India in relation to the global mariculture productivity would suggest that India could augment its marine exports by at least 20,000 MT by undertaking mariculture in sheltered bays, coves and backwaters in the Andaman seas alone.

It is estimated that by utilising 0.01 per cent of its 5.2 million hectare of continental shelf area under commercial cage fish farming in appropriate locations, an annual fish production of the order of 0.5 million tonnes could be achieved.

Aquaculture of high value finfish species, such as groupers, is of increasing importance throughout the Asia-Pacific region, including Australia. The development of large and affluent markets for live reef fish, particularly in Hong Kong and southern China, has increased pressure on fishery resources. In many areas the demand for live reef fish, and the profitability of this trade, has encouraged over fishing and the use of destructive fishing practices.

One such practice is the use of sodium cyanide to ‘stun’ reef fish for capture by divers. Because of the high toxicity of sodium cyanide, more fish are killed than are captured live and consequently coral reef areas are being devastated. Aquaculture of high value reef fish species can potentially supply product to the live reef fish markets, as well as other regional and domestic markets.

The development of aquaculture technology for these species will not only support an economically beneficial aquaculture sector but also contribute to reducing the pressure on fishery stocks.

IMPORTANCE OF MARICULTURE

Production of fish in India has grown at the rate of 5.71 per cent per annum during the Eighth Plan Period and at the rate of 2.18 per cent per annum during the Ninth Plan Period. This trend in production suggests that the growth rate in marine fish production showed a negative trend (-0.94 per cent) during the Ninth Plan as against a positive growth rate (3.93 per cent) during the Eighth Plan. The growth rate in inland fish production also reflects a deceleration at 5.6 per cent during the Ninth Plan as against the growth rate of 6.84 per cent during the Eighth Plan.

Viewed against this backdrop, the Government of India’s aim to increase the production of fish from 5.8 million tonnes to 8 million tonnes and export from Rs 6,000 crore to Rs 10,000 crore durduring the Tenth Plan Period may appear to be a stiff target. Therefore, the proposal is to achieve the target through stabilisation in marine fish production and doubling the production through aquaculture.

But it may not be possible to achieve this target through inland aquaculture since the untapped potential in the inland sector is 1.3 million tonnes, while the overall potential of the inland fish production is 4.5 million tonnes. It is in this context that mariculture assumes great importance for a country like India, which has not exploited the seaward side of its coastline for aquaculture.

However, in India, no systematic efforts have been made to even assess the potential of mariculture. Formulation of a leasing policy, identification of potential sites, standardisation of culture practices and implementation of projects remain a remote possibility. The multitude of permissions that an entrepreneur is required to obtain from a plethora of agencies often act as stumbling blocks in the absence of a clear policy.

THE FARMING SYSTEMS

Considering the recent developments in the fishery industry, five cage fish farming systems have been extensively promoted.

A traditional farming system using conventional feed and feeding mechanism (System 1): A wide variety of cage designs have been developed over the last 20 years for this type of farming. The common features in the various cage designs are a floating collar, usually rectangular, a suspended net bag and a mooring system.

The design of the cage comprises a square or rectangular frame of superstructure with walkways in between the rows of the cage. A steel handrail, about 0.75 m high, is attached to the inside of the walkway, and from this the cage bag is suspended.

Typically, the cages are connected to each other with ropes and shackles to form a floating rectangular raft of 15-20 individual cages with a central walkway. The raft is moored to the seabed or to the shore using anchors, chains, ropes and shock-absorbing systems.

The feeding system is considered to be an automatic feeder type based on a feeding program preset by the farmer to dispense the dry pellet. A 12V battery and a control unit regulate the feeding in the cages. The feeding is synchronised in all the cages using the timing device. In the traditional farming system, conventional feed with Feed Conversion Ratio (FCR) value of 1.5 is used.

Improved farming system using efficient feed and feeding mechanism (System 2): This farming system is similar to the earlier system except for the feeding mechanism, the type of feed used and the production programme. In this case an improved feed with an FCR value of 1.0 is considered. A strict feeding regime envisages use of computer aided ‘adaptive feeding system’ that controls automatic feeders by accurately matching feed delivery with the appetite of the fish.

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