Latin name – Crassostrea gigas
Taxonomic Code: 3160700801
Production (EU-27) – 142 000 t (2007), fourth highest production level worldwide
Value (UE-27) – EUR 295 million (2007)
Main EU producer countries – France (Europe’s top producer and fourth worldwide), Ireland, Spain, Portugal
Main producer countries worldwide (outside Europe) – China, South Korea, Japan.

Local Names
English : Giant oyster,  Giant Pacific oyster,  Immigrant oyster,  Japanese Oyster,  Miyagi oyster,  Pacific cupped oyster
French : Gigas,  Huitre géante du Pacifique
Spanish : Ostión,  Ostión japonés
Turkish : İstiridye

Diagnostic Features

Shell solid, inequivalve, extremely rough, extensively fluted, and laminated; left (lower) valve deeply cupped, its sides sometimes almost vertical, the right (upper) valve flat or slightly convex sitting withing left; inequilateral, beaks and umbones often overgrown; tending to be oblong in outline but often distorted and very irregular. The shape of the shell varies with the environment.  Color usually whitish with many purple streaks and spots radiating away from the umbo. The interior of the shell is white, with a single muscle scar that is sometimes dark, but never purple or black. 

Habitat and Biology

Is an exotic species introduced into west coast estuaries americaines from Japan. Prefer firm bottoms, and usually attach to rocks, debris or other oyster shellsat depths of between 5 and 40 m.However, they can also be found on mud or mud-sand bottoms.
Pacific oysters are protandrous hermaphrodites. They change sex, but their timing is erratic and seasonal. Spawning depends on a rise in water temperatures above eighteen degrees Celsius. When spawning does occur, it occurs primarily in July and August; eggs (50-100 millions in single spawning) and larvae are planktonic distributed throughout the water column in estuarine waters. Later stage larvae settle out of the water column and crawl on the bottom searching for suitable habitat before settling.  Juveniles and adults are sedentary and are found in lower intertidal areas of estuaries.

Market And Trade

Much of the production of the major producing countries is absorbed by domestic markets and is supplemented by imports from adjacent countries and trading partners (e.g. trade within the EU, where France imports surplus from other EU countries such as the United Kingdom and Ireland). The relatively short shelf life of this species is an impediment to large-scale global trade for fresh product, and consumer preference is often for live, half shell oysters or freshly shucked meats. Value-added and convenience products, including canned oysters and frozen or vacuum packed oysters prepared with various sauces, appear from time to time and have potential for global distribution. However, they represent only a small proportion of total production. There continues to be international marketing potential for hatchery-produced seed, particularly for triploids.

Status and trends

Worldwide aquaculture production of the Pacific cupped oyster continues to expand steadily, having expanded from 156 000 tones in 1950 to 437 000 tones by 1970, and 1.2 million tones by 1990. Expansion was very rapid in the 1990s, rising to 3.9 million tones by 2000. Expansion is continuing, reaching nearly 4.4 million tones by 2003. Production is likely to continue to expand, albeit at a slower rate due to coastal urbanization and the increasing need to share the common coastal resource with other users.

Main issues

Unlike many other species in aquaculture, the reliable supply of seed is not a constraint to further development. It is either readily available for capture in the wild or can be produced relatively inexpensively in massive quantity in hatcheries. Of great concern is the potential for environmental degradation, which already exists in some areas of major production, and also the potential for the Pacific oyster to out-compete and take over habitat occupied by indigenous bivalves in countries to which it has been introduced. Pacific oysters have great capacity to filter large volumes of seawater and thereby, in intensive culture, deposit large quantities of bio-wastes. They form dense reefs in areas where they breed naturally and the reefs act as sediment traps by slowing bottom water flow and at the same time altering biodiversity. Hanging culture methodology lessens these environmental impacts.

Introductions, whether deliberate or accidental, into New Zealand and New South Wales, Australia, have highlighted the potential to displace native species. Pacific cupped oysters were first positively identified in the Auckland area of North Island, New Zealand in 1971 By 1977 Crassostrea gigas had become the dominant farmed oyster, having displaced the native Rock oyster (Saccostrea glomerata), through competition for settlement space and by virtue of their greatly superior growth rate. Similarly, the accidental introduction or transfer of C. gigas into bays and estuaries in New South Wales, where an important aquaculture production of the native Sydney Rock oyster, Saccostrea commercialis, exists, has been treated with grave concern by producers, Government and environmentalists alike.



FAO. © 2005-2011. Cultured Aquatic Species Information Programme. Crassostrea gigas. Cultured Aquatic Species Information Programme. Text by Helm, M.M. In: FAO Fisheries and Aquaculture Department [online]. Rome. Updated 13 April 2005. [Cited 12 September 2011]. http://www.fao.org/fishery/culturedspecies/Crassostrea_gigas/en

http://ec.europa.eu/fisheries/marine_species/farmed_fish_and_shellfish/oysters/index_en.htm