Aquaculture Ascendant - Fish Farming Increases

By the end of the decade, fish farming may overtake cattle ranching as a food source.

by Lester R. Brown, 2000 Worldwatch Institute (C)

Aquaculture, growing at 11 percent a year over the past decade, is the fastest growing sector of the world food economy.

Climbing from 13 million tons of fish produced in 1990 to 31 million tons in 1998, fish farming is poised to overtake cattle ranching as a food source by the end of this decade.

This record aquacultural growth is signalling a basic shift in our diet. Over the last century, the world relied heavily on two natural systems–oceanic fisheries and range lands–to satisfy a growing demand for animal protein, but that era is ending as both systems reach their productive limits.

Between 1950 and 1990, beef production, four fifths of it from range lands, nearly tripled, climbing from 19 million to 53 million tons before plateauing. Meanwhile, the oceanic fish catch grew from 19 million to 86 million tons before levelling off. Since 1990, there has been little growth in either beef production or the oceanic fish catch.

Additional production of beef or seafood now depends on placing more cattle in feed lots or more fish in ponds. At this point, the efficiency with which cattle and fish convert grain into protein begins to reshape production trends and thus our diets.

Cattle require some seven kilograms of grain to add one kilogram of live weight, whereas fish can add a kilogram of live weight with less than two kilograms of grain.

Water scarcity is also a matter of concern, since it takes 1,000 tons of water to produce one ton of grain. But the fish farming advantage in the efficiency of grain conversion translates into a comparable advantage in water efficiency as well, even when the relatively small amount of water for fish ponds is included. In a world of land and water scarcity, the advantage of fish ponds over feed lots in producing low-cost animal protein is clear.

In contrast to meat production, which is concentrated in industrial countries, some 85 percent of fish farming is in developing countries. China, where fish farming began more than 3,000 years ago, accounted for 21 million tons of the 31 million tons of the world output in 1998. India is a distant second with two million tons. Other developing countries with thriving aquacultural sectors include Bangladesh, Indonesia, and Thailand.

Among industrial countries, Japan, the United States, and Norway are the leaders. Japan's output of 800,000 tons consists of high-value species, such as scallops, oysters, and yellowtail. The US output of 450,000 tons is mostly catfish. Norway's 400,000 tons is mostly salmon.

With over fishing now commonplace, developing countries are turning to fish farming to satisfy their growing appetite for seafood largely because the oceanic option is not available to them as it was earlier to industrial countries. For example, as population pressure on the land intensified in Japan, it turned to the oceans for its animal protein, using scarce land for rice. Today Japan's 125 million people consume some 10 million tons of seafood each year. If China's 1.25 billion were to eat seafood at the same rate, they would need 100 million tons–the global fish catch.

Although at least 220 species of fin fish, shellfish, and crustaceans are farmed commercially, a dozen or so dominate world output. Among fin fish, five species of carp–all widely grown in China–lead the way with a total output of some 11 million tons in 1998, more than one-third of the world aquacultural output. Among shellfish, the Pacific cupped oyster, at 3.4 million tons (including shell), dominates, followed by the Yesso scallop and the blue mussel.

In China, fish are produced primarily in ponds, lakes, reservoirs, and rice paddies. Some five million hectares of land are devoted exclusively to fish farming, much of it in carp polyculture. In addition, 1.7 million hectares of rice land is used to produce rice and fish together.

Over time, China has evolved a fish polyculture using four types of carp that feed at different levels of the food chain.

Silver carp and bighead carp are filter feeders, feeding on phytoplankton and zooplankton, respectively. The grass carp, as its name implies, feeds largely on vegetation, while the common carp is a bottom feeder, living on detritus that settles to the bottom. Most of China's aquaculture is integrated with agriculture, enabling farmers to use agricultural wastes, such as pig manure, to fertilize ponds, thus stimulating the growth of plankton. Fish polyculture, which can boost the fish yield per hectare over that of monocultures by half, also dominates fish farming in India.

As land and water become scarce, China's fish farmers intensify production by feeding more grain concentrates to raise pond productivity. Between 1990 and 1996, China's farmers raised the annual pond yield per hectare from 2.4 tons of fish to 4.1 tons.

In the United States, catfish, which require only 1.6 kilograms of feed to gain one kilogram of live weight, is the leading aquacultural product. With US catfish production last year at roughly 600 million pounds (270,000 tons), or more than two pounds for each American, US consumption of catfish exceeded that of lamb and mutton.

US catfish production is concentrated in four states: Mississippi, Louisiana, Alabama, and Arkansas. Mississippi, with 45,000 hectares of catfish ponds and 60 percent of US output, is the catfish capital of the world.

Among the aquatic species that are widely farmed, two can wreak environmental havoc: salmon, with production of 700,000 tons per year, and shrimp at 1,100,000 tons per year. Salmon are grown mostly in industrial countries, principally in Norway, for consumption in those countries. Shrimp are grown largely in developing countries, such as Thailand, Ecuador, and Indonesia, for export to more-affluent societies.

Salmon, a carnivorous fish, are fed a diet consisting mainly of fish meal, typically made from anchovies, herring, or the remnants of fish processing. In stark contrast to the production of herbivorous species, such as carp and catfish, which lighten the pressure on oceanic fisheries, salmon production actually intensifies pressure because it requires up to five tons of landed fish for each ton of salmon produced.

Another concern is that if farmed salmon, which are bred for fast growth and not for survival in the wild, escape because of damage to pens by storms or attacks by predators, such as harbour seals, they can breed with wild salmon, weakening the latter's capacity to survive. Fish grown in offshore cages or pens, as salmon frequently are, also concentrate large quantities of waste. For example, the waste produced by farmed salmon in Norway is about equal to the sewage produced by Norway's four million people.

Shrimp are often produced by clearing coastal mangrove forests which protect coastlines and serve as nurseries for local fish. Mangrove destruction can cause a decline of local fisheries that may exceed the gains from shrimp production.

A world that is reaching the limits for oceanic fisheries and range lands, while adding 80 million people per year, needs efficient new sources of animal protein. Herbivorous fish, such as carp grown in polycultures or in combination with rice, or catfish grown in ponds, offer an efficient way of expanding animal protein supplies in a protein-hungry world.

Fish farming is not a solution to the world food problem, but as China has demonstrated, it does offer a source of low-cost animal protein for lower-income populations.

* For additional data, contact: Reah Janise Kauffman; phone: (202)452-1992, ext. 514; fax: (202)296-7365;


Free-Roaming Fish

There were two large escapes of Atlantic salmon on the west coast in August of 2000, both from Stolt Seafarms. More than 32,000 fish escaped from a pen operated by the company in Johnstone Strait, off northwestern Vancouver Island. Earlier, the company lost about 4,500 Atlantic salmon from another operation near Campbell River.

The BC Fisheries Minister at that time, Corky Evans, said he would impose a "new regulatory regime" intended to enforce escape prevention plans; in October, 2000, the province introduced new regulations and approved four pilot projects that make use of green technologies.

Among the new regulations are extended stream surveys for Atlantic salmon and an increase in random audits. The four projects approved (of 13 proposed by the industry) are: Totem Oysters in Jervis Inlet, marine harvest (Nutreco) on Saltspring Island, Heritage Aquaculture and the Homalco Band in Bute Inlet, and the Kitasoo/Xiaxias First nations and Marine Harvest (Nutreco) in Jackson Passage, north of Bella Bella. These projects will test closed-containment systems with waste recovery, diets to reduce the use of fish meal, and a freshwater envelope to rear freshwater fry in the marine environment.

Safeguards recommended by the David Suzuki Foundation include: zero discharge of fish sewage, industry-developed and -funded site reclamation plans, mandatory insurance for operators to cover ecological restoration costs, and the elimination of fish that can be used for human food as feed for farmed salmon.

* More information from the BC government at: and from the David Suzuki Foundation at:


[From WS February/March 2001]

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