Ostrea angasi

Invasion History

First Non-native North American Tidal Record:
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record:

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General Invasion History:

Ostrea angasi is native to the southern coast of Australia, from New South Wales and Tasmania to Fremantle, Western Australia (Carriker and Gaffney 1996; Morton et al. 2003). This oyster is well-regarded as food in Australia, and has been tested as a possible aquaculture oyster in California and France. However, it did not survive in any of these locations (Carlton 1979; Goulletquer et al. 2002).

North American Invasion History:

Invasion History on the West Coast:

Experimental plantings of small numbers of O. angasi were made in San Francisco Bay, at Redwood City in 1962, and later in Tomales Bay and Drakes Bay. None of these oysters survived for more than a year (Hanna 1966; Carlton 1979).

Invasion History Elsewhere in the World:

Ostrea angasi was introduced in oyster beds at Crach and Etel, Brittany, in 1985, as a possible substitute for depleted stocks of O. edulis. However, these oysters suffered rapid mortality due to Bonamia spp., other haploporidian parasites, and the protozoan Marteilia refringens (Bougrier et al. 1986; Goulletquer et al. 2002).

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Description

Ostrea angasi has a roughly triangular to oval shell, with a slightly hooked beak. The upper (right) valve tends to be heavily eroded, exposing calcareous layers. The outer margin bears conspicuous, concentric brown lamellae (layers) on the outer surface. The left shell is concave and fixed to the substratum. The shells are heavily bored by polychaetes and encrusted with barnacles. The region near the hinge lacks chomata (fine crenulations, which do occur in O. edulis). The interior of the shell has white to blue-green patches of nacre. The muscle scar is crescent-shaped and located in the posterior-ventral third of the pallial area (the scar is more centrally located in O. edulis). The similarity of O. angasi and O. edulis is so great that molecular identification is necessary for reliably separating the two species (Morton et al. 2003). Larvae settled at 300-320 µm (Dix et al. 1976). Large adults in a growth experiment reached a mean of 102 mm length (Mitchell et al. 2000), but the maximum size is probably larger.

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Taxonomy

Ecology

General:

Ostrea angasi, like other oysters, is a protandric hermaphrodite, maturing first as a male and then becoming female in subsequent seasons. Males release sperm, into the water column, while females brood eggs in their gills, where fertilization occurs. Larvae are brooded and released as shelled veligers. Each veliger feeds on phytoplankton, and grows, eventually developing a foot and becoming a pediveliger, competent for settlement. In laboratory culture, larval settlement occurred at about 12-20 days at 17⁰C (Dix 1976). Adult oysters grow to at least 100 mm (Mitchell et al. 2000). Ostrea angasi is characteristic of coastal waters in southern Australia. This oyster normally grows at marine salinities, but adults can tolerate a range of 20-45 PSU (Dix 1976).

Food:

Phytoplankton

Consumers:

birds, fish, crabs, parasites, humans

Trophic Status:

Suspension Feeder

SusFed

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Habitats

General Habitat	Oyster Reef	None
General Habitat	Marinas & Docks	None
General Habitat	Rocky	None
General Habitat	Unstructured Bottom	None
Tidal Range	Subtidal	None
Tidal Range	Low Intertidal	None
Vertical Habitat	Epibenthic	None

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Tolerances and Life History Parameters

Minimum Salinity (‰)	20	Experimental (Nell and Gibbs 1986)
Maximum Salinity (‰)	45	Experimental (Nell and Gibbs 1986)
Minimum Duration	12	Time from larval release to settlement, at 17 C (Dix 1976)
Maximum Duration	20	Time from larval release to settlement, at 17 C (Dix 1976)
Broad Temperature Range	None	Warm temperate-Subtropical
Broad Salinity Range	None	Polyhaline-Euhaline

General Impacts

Ostrea angasi was harvested and depleted in southern Australia by the early 20th century, but there has been periodic interest in its culture in Australia. However, cultured populations in Australia were subject to a variety of diseases, limiting the extent of culture. Attempts to introduce this oyster to California and France failed due to high mortality (Hanna 1966; Carlton 1979; Bougrier et al. 1986; Goulletquer et al. 2002).

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References

Bougrier, S.; Tige, G.; Bacher, E.; Grizel, H. (1986) Ostrea angasi acclimatization to French coasts, Aquaculture 58: 151-154

Carlton, James T. (1979) History, biogeography, and ecology of the introduced marine and estuarine invertebrates of the Pacific Coast of North America., Ph.D. dissertation, University of California, Davis. Pp. 1-904

Carriker, Melbourne R.; Gaffney, Patrick M. (1996) The Eastern Oyster Crassostrea virginica, Maryland Sea Grant, College Park MD. Pp. <missing location>

Dix, Trevor G. (1976) Laboratory rearing of Ostrea angasi in Tasmania, Australia, Journal of the Malacological Society of Australia 3(3-4): 209-214

Goulletquer, Philippe; Bachelet, Guy; Sauriau, Pierre; Noel, Pierre (2002) Invasive aquatic species of Europe: Distribution, impacts, and management, Kluwer Academic Publishers, Dordrecht. Pp. 276-290

Hanna, G. Dallas (1966) Introduced mollusks of Western North America, Occasional Papers of the California Academy of Sciences 48: <missing location>

Leitâo, Alexandra and 5 authors HENRIQUE GUEDES-PINTO,2 AND CATHERINE TIDRIOT-QUIÉVREUX3* (2002) Cytogenetic study of Ostrea conchaphila (Mollusca: Bivalvia) and comparative karyological analysis within Ostreinae, Journal of Shellfish Research 21(2): 685-690

Li , X. X.; Havenhand, J. N. (1997) Karyotype, nucleolus organiser regions and constitutive heterochromatin in Ostrea angasi (Molluscae: Bivalvia): evidence of taxonomic relationships within the Ostreidae, Marine Biology 127: 443-448

Mitchell, Iona M.; Crawford, Christine M.; Rushton, Michael J. (2000) Flat oyster Ostrea angasi growth and survival rates at Georges Bay, Tasmania, Australia, Aquaculture 191: 309-321

Morton, Brian; Lam, Katharine; Slack-Smith, Shirley (2003) First report of the European Flat Oyster (Ostrea edulis) identified genetically from Oyster Harbour, Albany, south-western Western Australia., Molluscan Research Molluscan Research 23: 199-208

Nell, J. A.; Gibbs, P. J. (1986) Salinity tolerance and absorbance of L-Methionine by some Australian bivalve mollusks, Australian Journal of Marine and Freshwater Research 37: 721-727

Nell, John A. (2001) The history of oyster farming in Australia., Marine Fisheries Review 63(3): 14-25

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