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|  | | Production is largely derived from land-based freshwater culture systems. These continue to have considerable potential for further expansion, particularly the multiple resource use systems that are integrated with agriculture and irrigation. The marine environment offers resources for aquaculture which remain largely to be explored.A wide variety of animal and plant species are produced through aquaculture: finfish; shrimp, prawns and crabs; clams,oysters and mussels; as well as seaweeds and .other aquatic plantsAquaculture provides about one third, or 40 million metric tonnes, of the annual world fisheries production of 120 million metric tonnes. Half of all aquaculture production is finfish, a quarter is aquatic plants and the remaining quarter is made up of crustacea (such as shrimp, prawns, crabs) and molluscs such as clams, oysters and mussels.The most harvested species in recent years has been the Pacific Oyster (Crassostrea gigas), which grossed 3.4 million metric tonnes in 1998. The Pacific Oyster was the number one aquaculture species in four out of the five years to 1998.A close second is a freshwater fish, the Silver Carp (Hypophthalimichthys molitrix) which contributes more than 3 million metric tonnes per year to world totals. Silver Carp are grown in ponds, mainly in Asia, and eat tiny plankton. In the early 1990s they were the world's leading aquaculture species, until 1994 when the Pacific Oyster took over. Given its higher yield of meat compared to the oyster, it is arguable that the Silver Carp is still the world's most important aquaculture species.Seven out of the ten top species are freshwater finfish and six of those are carps. The other three species figuring in the top ten are molluscs.Carps accounted for nearly half of the 31 million metric tonnes of fish and molluscs produced by farming in 1998. Molluscs also made a major contribution (9.1 million mt) while production of farmed salmon, tilapia and shrimp totaled around 1 million metric tonnes each. Herbivores outnumber carnivores about ten to one in world aquaculture production.The Top Ten Species Produced by Aquaculture (1998)Pacific OysterCrassostrea gigasSilver CarpHypophthalmicthysmolitrixGrass carpCtenopharyngodonidellusCommon CarpCyprinus carpioBighead CarpHypophthalmicthysnobilisJapanese Carpet ShellRuditapesphilippinarumCrucian CarpCarassiuscarassiusYesso ScallopPecten yessoensisNile TilapiaOreochromisniloticusRoho CarpLabeo rohitaThe aquatic plants produced include brown, red and green seaweeds, grown for direct use as food and also for the extraction of alginate and carageenan (agar-agar). Half of the total 1998 production was of just one species, the Japanese Kelp (Laminaria japonicus), 90 percent of which is grown in China.Freshwater fish are the most important aquaculture group by volume and make the greatest contribution to the human food supply. However, some of the minor product groups such as shrimp and marine fish have a disproportionate economic importance because of their high unit value. Farmed freshwater fish, for instance, had an average value of US$1.14 per kg in 1998, while marine fish came in at US$4.35 and crustacea at US$5.90 per kg.Overall most of the major aquaculture product groups exhibited a two- to three-fold growth during the 1990s with some individual species increasing even more. World production of the Chinese River Crab (Eriocheir sinensis), for example, expanded twenty-five fold between 1989 and 1998 (from 5 000 to 123 000 mt). Other notable increases include the Giant Freshwater Prawn (Macrobrachium rosenbergii) with a six-fold growth, the Black Carp (Mytopharyngodon piceus) with a 4-fold growth and the Japanese Carpet Shell (Ruditapes philippinarum) with a 5-fold growth. The sector of high value marine finfish (such as seabass, grouper and mandarin fish) is also experiencing a strong expansion driven by demand in affluent Asian markets, especially for the live product. | | | | |
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