The protein requirement of an average individual is estimated as 0.72g/kg/day (Institute of Medicine of the National Academies IMNA, 2005) which works out to 13.14 kg for a 50 kg person/year.

Hence the country’s current protein requirement to feed its 1.27 billion populations is approximately 16.69 mmt.

With one third of the Indian population preferring a vegetarian diet and considering that the protein requirement of 60 per cent of its non-vegetarian population is also met by plant resources, the animal protein requirement of the country is estimated to be 4.45 mmt.

To achieve the world’s average fish protein contribution of 16 per cent (Central Statistical Organization-Manual on Fishery Statistics, Ministry of Statistics and programme implementation CSO-MFS, 2011) in the total animal protein production (4.45 mmt) we need to generate 0.71 mmt of fish protein in our country.

Bearing in mind the average protein content of fish (15 to 30 g /kg), to meet the present protein requirement of the nation we need to produce 31.64 mmt of fish against the current 8.8 mmt production.

The country’s marine capture fishery has attained its maximum sustainable yield of 3.97 mmt out of the estimated revised fishery potential of about 4.5 mmt and there is no further scope to increase its productivity.

It is estimated by Food and Agriculture Organization (FAO) that around 20 per cent of the total fish production of the world comes from capture-based aquaculture and that this practice needs to be encouraged and regulated for sustainable fish production (The State of World Fisheries and Aquaculture SOFIA, 2012).

However, fresh and brackish water culture has its own limitations and cannot be expanded beyond a certain level without harming the environment. The only possibility to meet the present demand is by farming in the seas with recent technologies for which India is yet to frame its sea leasing policy.

The production of farmed aquatic organisms in caged enclosures has been a relatively recent aquaculture innovation. The cage aquaculture sector has grown rapidly during the past decades and is presently undergoing changes in response to pressures from globalization and growing demand for aquatic products in both developing and developed countries. The opportunities for cage culture to provide fish for the world’s growing population are enormous, and particularly so in marine waters.

In three decades (1980 -2010), world food fish production by aquaculture has expanded 12 times over, at an average annual rate of 8.8 per cent and Indian aquaculture has demonstrated a six and half fold growth over just two decades, with freshwater aquaculture contributing over 95 percent of the total aquaculture production (SydaRao, 2009 ‘Overview on mariculture and the opportunities and challenges of cage culture in India’, National Fisheries Development Board).

The need to improve fish production capabilities of the country which is bestowed with 7,517 km long coast line, 2.02 million sq. km of exclusive economic zone (EEZ) and 5.3 lakh sq km  of continental shelf is very convincing.

Despite the huge potential, the development of large scale mariculture in the country is yet to kick off. The major barriers in offshore farming are—lack of sturdy cages and anchoring protocols to withstand turbulent open seas; commercial production of marine finfish seeds; lack of nursery rearing systems to supply stockable size seeds for open sea cage culture; availability of formulated species specific feeds; and above all legislative support for fish culture in the sea.

The National Institute of Ocean Technology (NIOT) under the Ministry of Earth Seances (MoES), with its expertise in marine engineering and aquatic biology decided to address the prime issue of designing a culture system for mariculture operation both at nearshore and offshore areas along with standardisation of mooring configurations. While appreciating the vastness of the Indian seas and its ideal tropical climate for fish farming, the rough sea conditions, high water currents, absence of shore landing facilities are points to ponder when designing sea cages.

Taking into considerations the nuances of sea farming, the Institute has custom designed high-density polyethylene (HDPE) cages (9 m in diameter) and fabricated and deployed them with multipoint grid mooring system in three different environments that represent the country’s prime marine ecosystems.

These cages are presently being tested by growing various marine finfish species obtained from hatcheries as well as from the wild. In order to assess the mariculture potential of the country, a geospatial analysis was carried out for the entire EEZ of the country involving ten vital physical parameters—depth, Sea Surface Current, Wave Height, Total Suspended Matter, and chemical parameters—sea surface temperature, salinity, dissolved oxygen, nitrate, phosphate and biological chlorophyll-‘a’.

This revealed a huge suitable sea space (3,18,456 km2) available for taking up sea farming in the country. Based on the results of the analysis the 0-100 depth zone across the coastline of the country were classified into three categories as no farming (up to 5 m depth), community farming (5-20 m depth) and industrial farming (20-100 m depth) zones.

Though the cages developed could withstand the sea conditions during the last five years of deployment, accessing these cages in rough weather with no shore landing facility or jetty was difficult. Hence, the need for automated cage with shore control and offshore platform based facilities arose in order to ensure year round culture.

There is no established system for taking care of nursery rearing in a large scale to provide stockable size fish seeds. The infrastructure available for fish seed production are insufficient when compared to the country’s huge requirement and out of the 80+ species of marine finfishes standardised worldwide for aquaculture, research is limited to a single species (Latescalcarifer) with a production capability of mere 5 million fry/year.

As part of the cage development initiatives, the NIOT has designed and developed a sea based nursery cage with a diameter of 2 m for rearing as small as 5 g size marine finfishes and demonstrated the nursery rearing of seabass fingerlings of 5-6 g to 30 g size with 90 per cent survival in 45-50 days both at Kothachathram (Andhra Pradesh) and Olaikuda (Tamil Nadu) in open sea conditions.

These cages will greatly reduce the difficulty in getting the stockable size fish seeds and transporting the bigger fish seeds to the sea cages. Further, the infrastructure requirement for a land based nursery rearing facility for rearing a million fish seed is estimated as 20,000 m3 of constructed area (at a stocking density 50/m3) which can also be avoided. The Institute’s cage culture demonstration empowered the traditional fishermen of North Bay (Andamans), Olaikuda (Tamil Nadu) and Kothachathram (Andhra Pradesh) with hands on training in various aspects of cage farming right from cage fabrication to fish harvesting.

To produce 1 mmt of marine finfish we need to establish industries for the production of 1,00,000 grow out cages with 400 cu.m cultivable area and 3,00,000 units of nursery cages. Hatcheries should be established for the production of 1,500 million seeds of 5 g size with different finfish species suitable for the Indian seas.

Fish feed industries should be created with the capacity of 1.5 mmt including 0.02 mmt of nursery feed production units. We also require allied fishery industries for fish processing and storage apart from scientific and skilled manpower. Above all, it is mandatory to have a sea leasing policy in place to ensure the safety of the cultured products in the sea, which may also motivate private entrepreneurs to venture into sea farming.

The state governments may demarcate certain zones for sea farming activities after conducting a feasibility survey. Considering the above facts a plan for the production of 1 mmt fish through mariculture has been conceived by NIOT and submitted to the MoES for consideration. The Ministry has constituted a Working Group over the proposed plan involving the major stakeholders of the industry for the formulation of an implementable aquaculture strategy for the country.

Cage culture of milkfish with seeds from the vicinity was initiated by MoES on June 25, 2013 at Olaikuda fishing village. The cage culture demonstration empowered the traditional fishermen of Olaikuda and Kothachathram with hands-on training in various aspects of cage farming including fabrication, deployment, net maintenance, seed stocking, feeding, disease control measures, harvesting, etc. This capacity building in cage farming may help generate alternative livelihood strategies.

Out of the more than 200 commercial marine food fishes available in the country, only a few species are being attempted for hatchery production and only Latescalcarifer and Rachycentron canadum are being produced on a commercial scale by the Rajiv Gandhi Centre for Aquaculture, the Central Institute of Brackishwater Aquaculture and the Central Marine Fisheries Research Institute.

To initiate large scale fish production a country-wide survey needs to be initiated to know the seasonal wild seed availability of potential species. The NIOT conducted a local survey around Rameswaram to take stock of the milkfish seed availability and found that along with mullets it was abundant around the Gulf of Mannar region between March and August. The region is also bestowed with rabbit and parrot fish seeds; rearing them in sea cages yielded encouraging results.

Despite the lack of reliable statistical information of cage aquaculture globally, a growing trend is evident in the segment. Brackishwater and marine cage farming is relatively new in Asia, having developed first in Japan for the Japanese amperjack (Seriolaquinqueradiata). Over the last two decades, marine finfish aquaculture, predominantly cage farming, has spread throughout Asia with China and Vietnam mostly relying on wild collection for fish seed and feed (S S De Silva, et.al. 2007 ‘A review of cage aquaculture: Asia excluding China’, Cage aquaculture-Regional reviews and Global overview, FAO Fisheries Technical Paper).

Considering the advancements that cage culture has made in countries such as Norway and Chile in terms of reduced antibiotics usage and prevention of feed loss, with improved feeds and feeding techniques, there is a possibility that this sector will contribute significantly to the protein needs of the world’s growing population. Developing sea farming or cage culture is thus an achievable and potential strategy to India.