Ostreola conchaphila

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The Ostreola conchaphila is commonly known as the Olympia oyster. This oyster is native to the Pacific coast of North America from Alaska to Mexico. These oysters are called Olympia oysters after the important 19th century oyster industry near Olympia, Washington, in Puget sound.

Ostereola conchaphila
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Ostreoida
Family: Ostreidae
Genus: Ostreola
Species: O. conchaphila
Binomial name
Ostreola conchaphila
Carpenter, 1857



Oysters are filter feeders, drawing water in over their gills through the beating of cilia. Suspended plankton and particles are trapped in the mucus of a gill, and from there are transported to the mouth, where they are eaten, digested and expelled as faeces or pseudofaeces. In addition to their gills, oysters can also exchange gases across their mantle, which is lined with many small, thin-walled blood vessels. A small, three-chambered heart, lying under the adductor muscle, pumps colorless blood to all parts of the body. At the same time, two kidneys, located on the underside of the muscle, remove waste products from the blood. One characteristic that is unique to Olympia oysters is that they have two sexes, their reproductive organs contain both eggs and sperm. This allows Olympia Oysters to technically have the possibility to fertilize its own egg. Once fertilized, they discharge millions of eggs into the water. The larvae develop in about six hours and swim around for about two to three weeks. After that, they settle on a bed and mature within a year. (1)

Description and Habitat

The average size of an Olympia oyster is 50 mm. The size refers to shell length only and gives the largest average size. Olympia Oysters are usually found on rocky substrates near the low tide line or on mud flats and gravel bars in quiet bays with low salinities. (2) A group of these or any other oysters is commonly called a bed or oyster reef. These oyster reefs actually provide habitat for many other marine species. The hard surfaces of these oyster shells and the nooks between the shells provide places where a host of small animals can live. Hundreds of animals such as sea anemones, barnacles, and hooked mussels inhabit these oyster reefs.(1)

Functions and Uses

Olympia Oysters as well as oysters in general consume nitrogen-containing compounds (nitrates and ammonia), removing them from the water. Nitrogen compounds are important phytoplankton nutrients. Phytoplankton increase water turbidity. Limiting the amount of phytoplankton in the water improves water quality and other marine life by reducing competition for dissolved oxygen. Oysters feed on plankton, incidentally consuming nitrogen compounds as well. They then expel solid waste pellets which decompose into the atmosphere as nitrogen. (1)

Olympia Oysters are also used for human consumption. The importance of oysters as a food in many cultures dates back as far as prehistoric Roman and early United kingdom traditions. "Oysters, especially 'wild', are excellent sources of several minerals, including iron, zinc and selenium, which are often low in the modern diet. They are also an excellent source of Vitamin B12. Oysters are considered the healthiest when eaten raw on the half shell." Jonathan Swift. Olympia oysters in particular proved extremely important for the Native Americans on the west coast. American peoples consumed O. conchaphila everywhere it was found, with consumption in San Francisco Bay so intense that enormous middens of oyster shells were piled over thousands of years. (3)


Ostreola conchaphila nearly disappeared from San Francisco Bay following overharvest during the California Gold Rush (1848-50s) and massive silting from hydraulic mining in California's Sierra Nevada (1850s-1880s). California's most valuable fishery from the 1880s-1910s was based on imported Atlantic oysters, not the absent native. But in the 1990s, O. conchaphila once again appeared in San Francisco Bay, surprisingly in some of the most polluted waters of the bay near the Chevron Richmond Refinery in Richmond, California. Currently the Olympia oyster populations have been decimated by overfishing, introduced species, habitat loss, and disease. (4)


Species restoration projects for the Olympia oyster funded by the U.S. Government are active in Puget Sound and San Francisco Bay.[2][3] An active restoration project is taking place in Liberty Bay, Washington.[4] This Puget Sound location is the home of an old and new Olympia oyster population. The re-establishment of the population is currently threatened by the invasive Japanese oyster drill Ocinabrina inorata. This species preys on the oysters by drilling a hole between the two valves and digesting the oyster's tissues. O. inorata is a threat to the oyster especially in areas with low populations of the mussel Mytilis. The Nature Conservancy of Oregon also has an ongoing restoration project at Netarts Bay, Oregon.[5] (3)

(1) http://en.wikipedia.org/wiki/Oyster#Habitat_and_behaviour (2) http://nikmolnar.com/nathist/animalia/mollusca/bivalvia/ostereoida/ostreidae/ostreola/ostreola-conchaphila (3) http://en.wikipedia.org/wiki/Olympia_oyster (4) RestoringSouthern California Estuaries through Public-Private Partnerships: Developing Sustainable Aquaculture for an Ecosystem Engineer, the Native California Oyster, Ostreola conchaphila Group Project Proposal 2007