Fishing rights continue to be the cause – or at least the focus – of maritime territorial disputes in Asia, giving opportunities for nationalists to blow their trumpets. But the economic reality is that marine fisheries are becoming a less and less important contributor to global food supply, and for Asia in particular.

Already, according to the latest World Review of Fisheries and Aquaculture published by the UN Food and Agriculture Organization, almost half the fish now consumed by humans in the world are the product of aquaculture.

As for the half accounted for by capture fish, a decreasing proportion comes from the seas and an increasing one from fresh waters, particularly in Asia which accounts for some 70 percent of global inland capture fish with China, India, Myanmar and Bangladesh leading the way. (Although some of this is from waters which are artificially re-stocked)

Overall there is good news and bad news in the FAO report. The good news, particularly for Asia, has been the dramatic growth of aquaculture, particularly of freshwater fin fish species. The continent now account for 89 percent of global aquaculture by volume. At 36 million tons in 2010 China accounts for a little over half the Asian total, but others are now expanding faster with Vietnam at 2.6 million tons, Indonesia at 2.3 million, Bangladesh at 1.3 million and Thailand at 1.2 million. Some other countries appear to lag including the Philippines at just 740,000 tons despite a long history of bangus and other fish cultivation. China provided an especially fine example, now being followed elsewhere, notably Indonesia of combining fish farming with paddy production on a large scale. About one third of farmed fish are fed naturally but the percentage is declining.

Aquaculture, especially of shrimps and bi-valves, continues to create environmental issues and sometimes to be subject to outbreaks of disease which can cripple production. However, it is the only way to go given that global production of marine fish has peaked out and is more likely to decline than recover thanks to overfishing.

According to the FAO only about 10 percent of the world’s waters are now viewed as under-exploited while about 30 percent are over-exploited. Recent years have seen stagnation in the output from Asia and the world’s most productive waters – the northwest Pacific – at 20 million tons annually, or about 26 percent of the global marine catch. Japanese and Korean fishing fleets, as measured by tonnage, have been falling and China’s have stabilized.

The only two growth areas in the region have been the western central Pacific, now yielding nearly 12 million tons, and the eastern Indian ocean, now at 7 million tons. But the potential for further increases is believed to be minimal if they are not to become seriously over-fished. Although the FAO report does not say so, this may be a particular problem for Thailand which is a major exporter of marine fish – third in the world after China and Norway and ahead of Vietnam despite having an aquaculture sector half that of Vietnam. Thailand neighbors are also becoming more aware of the need to protect their marine fishing rights. Thailand is the major exporter of tuna which comprises 8 percent of global fish trade. It has also been a particular problem for the Philippines, where both domestic and international purse seiners have largely fished out the rich tuna resources off southern Mindanao (read: The Rise and Possible Fall of the Philippines' Tuna Capital).

The growth is likely to remain in aquaculture not deep sea fishing. Prices for increasingly scarce wild species like types of tuna have been rising but competition is strong in the aquaculture sector and prices in real terms have tended to fall. Nonetheless the importance of fish trade to developing countries exceeds that of several other agricultural products combined. Net developing nation exports are running at some US$25 billion and seem likely to continue to rise as fish increases its share of global protein consumption.

However the real goal for many Asian countries such as Bangladesh, the Philippines and Myanmar must be to increase fish production as a sure way of improving local nutrition.