The net is cast on agriculture

From an activity that was primarily confined to Asia, aquaculture is developing, expanding and intensifying worldwide, except in sub-Saharan Africa. This is evident as nearly half the fish consumed as food worldwide are raised on fish farms rather than caught in the wild, says a new report by UN's Food and Agriculture Organization

In 2004, global production of farmed fish was about 60 million tonnes. Of this 41.3 million tonnes (59 per cent) was produced in China and 22 per cent from the rest of Asia and the Pacific region

Of the total production, human beings consume about 45.5 million tonnes of farmed fish, worth us $63 billion each year. Currently, freshwater and marine capture fisheries produce 95 million tonnes annually, of which 60 is for human consumption

World aquaculture has grown at an average annual rate of 8.8 per cent from 1950 to 2004. Latin America and the Caribbeans had the highest rate of 21.3 per cent

Most aquaculture production consists of exotic species. The total production of Nile tilapia in Asia and the Pacific was 1.2 million tonnes in 2004 , as against 212,000 tonnes in places where it is native

Globally, demand for fish is climbing. Over 40 per cent of fish production is traded across borders and exports exceed that of meat, dairy, cereals, sugar and coffee

2004, developed countries imported 33 million tonnes of fish worth over us $61 billion -- 81 per cent of all fish imports that year

However, the levels of captures of fish in the wild have remained roughly stable since the mid-1980s, hovering around 90-93 million tonnes annually mainly due to declining fish population in wild.

But demand for fish is not just for humans. Since 1985, world production of fishmeal and fish oil has stabilised at 6 to 7 million tonnes and one million tonnes. The vast bulk of fishmeal is used for livestock feed, chiefly by the poultry sector. Aquaculture now accounts for 35 per cent of the world's fishmeal consumption

Besides economic benefits, trade in aquaculture commodities carries the risk of spreading aquatic animal pathogens. One example is the koi herpes virus. Since first being reported in Indonesia in 2002, the disease has spread to several countries

Aquaculture produces wastes which affect the environment. Intensive aquaculture produces large amounts of organic wastes and nutrients and if not managed properly pollutes water bodies

To maintain current levels of consumption given projected population growth, 40 million tonnes more of aquatic food will be needed annually by 2030. The only option: farming

A bottleneck is lack of capital for producers in the developing world. So are shortage of land and freshwater, and rising energy costs. Questions of  product safety also need attention