{{Short description|Species of oyster endemic to southern Australia}} {{Use Australian English|date=November 2020}} {{Use dmy dates|date=November 2020}} {{Speciesbox | image = Naturalis Biodiversity Center - RMNH.MOL.319376 2 - Ostrea angasi Sowerby, 1871 - Ostreidae - Mollusc shell.jpeg | image_caption = | genus = Ostrea | species = angasi | authority = Sowerby, 1871 }} The '''southern mud oyster''', '''Australian flat oyster''', '''native flat oyster''', '''native mud oyster''', or '''angasi oyster''' (''Ostrea angasi''), is endemic to southern [[Australia]], ranging from [[Western Australia]] to southeast [[New South Wales]] and around [[Tasmania]]. ''Ostrea angasi'' superficially resembles ''[[Ostrea edulis]]'' and both species may be referred to with the name "flat oyster". However, the two species do not occur naturally in the same geographic distribution.
==Habitat== This species is found in sheltered, silty or sand-bottomed [[estuaries]] at depths between 1 and 30 metres.
==Diet== Flat oysters, like all other [[oyster]] species, are [[filter feeder]]s, feeding on, and taking in anything small enough to be filtered in their [[gills]]. This may include [[plankton]], [[microalgae]] or [[inorganic]] material.
== Predators == Oyster growers at [[Coffin Bay (South Australia)|Coffin Bay, South Australia]] have observed stingrays eating their experimental commercial stocks of ''Ostrea angasi''.<ref name=":0">{{Cite news|url=http://www.abc.net.au/news/2014-06-14/high-export-hopes-for-forgotten-native-angasi-oyster/5520672|title=High export hopes for forgotten native Australian oyster|date=2014-06-14|newspaper=ABC News|access-date=2017-02-23|language=en-AU}}</ref>
==Commercial harvesting== Extensive oyster reefs in southern Australia were largely destroyed by over-exploitation during the 19th and early 20th Centuries. Oysters were dredged directly from the seabed.<ref>[http://nla.gov.au/nla.news-article43810616 National Library of Australia > Trove]: Oyster beds. ''[[South Australian Register]]'', 15 December 1884. P 4. Accessed 8 May 2015.</ref><ref>Alleway, H. K. and Connell S.D. (2015): Loss of an ecological baseline through the eradication of oyster reefs from coastal ecosystems and human memory. ''[[Conservation Biology (journal)|Conservation Biology]]'', [[Society for Conservation Biology]]. DOI: 10.1111/cobi.12452</ref>
Once common, O''strea angasi'' became locally extinct, in oyster-producing estuaries on the East Coast north of the [[Clyde River (New South Wales)|Clyde River]], as a result of the accidental introduction of the mud worm, ''Polydora websteri'', from New Zealand, in 1888 to 1898. The mudworm and silting ended all sub-tidal oyster production in New South Wales and Southern Queensland, and the oyster industry there became totally dependent upon inter-tidal production of another indigenous oyster, the Sydney rock oyster, ''[[Saccostrea glomerata]]''.<ref>{{Cite web |last=Nell |first=John |date=July 2007 |title=PRIMEFACT 590: Controlling mudworm in oysters |url=https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0010/637633/Controlling-mudworm-in-oysters.pdf |website=NSW Department of Primary Industry}}</ref><ref>{{Cite journal |last=Roughley |first=T.C. |date=1929 |title=The Story of the Oyster - Its History, Growth, and Cultivation in New South Wales |url=https://rosetta.slv.vic.gov.au/delivery/DeliveryManagerServlet?dps_func=stream&dps_pid=FL2034291 |journal=Reprinted from Australian Museum Magazine |volume=2 |issue=1925 |via=State Library of Victoria}}</ref>
In the 21st century, commercial oyster growers in southern [[Australia]] have started experimentally [[oyster farming|farming]] ''O. angasi'' as a means to diversify their businesses. This was prompted by other growers suffering massive stock losses of introduced Pacific oyster, ''[[Pacific oyster|Crassostrea gigas]]'', resulting from outbreaks of Pacific Oyster Mortality Syndrome (POMS)''.''<ref name=":0" />
== Not-for-profit projects ==
=== Port Adelaide River estuary === The not-for-profit organisation [[Estuary Care Foundation]] was established in [[South Australia]] to undertake trials growing ''Ostrea angasi'' in the [[Port River]] and adjacent waters.<ref>{{Cite web|url=https://estuary.org.au/projects-info/#shellfish-restoration|title=Estuary Care Foundation – Shellfish Restoration|website=estuary.org.au|access-date=2019-12-09}}</ref> The organisation is also involved in [[seagrass]] monitoring and restoration work within the Port River.<ref>{{Cite web|url=https://lefevre.noticeboard.net.au/estuary-care-foundation-sa-inc/estuary-care-foundation-news-and-milestones/|title=Estuary Care Foundation: News and Milestones {{!}} LeFevre NoticeBoard|language=en-US|access-date=2019-12-09}}</ref><ref name="estuarycare">{{cite web | title=Barker Inlet and Port River Estuary| website=[[Estuary Care Foundation]] | url=https://www.estuary.org.au/the-estuary/ | access-date=23 November 2020}}</ref> Estuary Care Foundation now operates as '''Friends of Port River'''. Around 2022 the Estuary Care Foundation '''Rigid Oyster Basket''' project as taken up by '''OzFish Unlimited''', via the (now) OzFish Adelaide & Fleurieu Chapter. Larger scale deployment of the ROBs in the Port Adelaide Inner Harbour is scheduled for early 2025.
=== Windara Reef === [[Windara Reef]] was constructed in [[Gulf St Vincent]], offshore from [[Ardrossan, South Australia|Ardrossan]], to promote the reestablishment of ''Ostrea angasi''.<ref>{{Cite web|url=https://yorkepeninsula.com.au/windara-reef|title=Windara Reef|website=Yorke Peninsula Tourism|language=en|access-date=2019-12-09}}</ref> The reef was also opened to recreational fishers in 2017.<ref>{{Cite web|url=https://pir.sa.gov.au/fishing/recreational_fishing/windara_reef|title=Windara Reef|last=Department of Primary Industries and Regions|first=South Australia|date=2017-08-21|website=pir.sa.gov.au|language=en-au|access-date=2019-12-09}}</ref> As of April 2019, it was the largest shellfish reef restoration project in the southern hemisphere. [[The Nature Conservancy]], the [[Government of Australia|Australian Government]], the [[Government of South Australia|South Australian Government]], the [[Yorke Peninsula Council]], The [[University of Adelaide]] and the [[Ian Potter Foundation]] have each contributed to funding the project.<ref>{{Cite web|url=https://pir.sa.gov.au/primary_industry/aginsight/news_feed/50000_oysters_find_new_home_at_windara_reef|title=50,000 oysters find new home at Windara Reef|last=Department of Primary Industries and Regions|first=South Australia|date=2019-04-12|website=pir.sa.gov.au|language=en-au|access-date=2019-12-09}}</ref>
=== Georges River and Botany Bay === It was announced, in 2023, that work would begin on re-establishing three sub-tidal oyster reefs in the [[Georges River]] estuary in New South Wales (at Audrey Bay, Coronation Bay and on the eastern side of [[Taren Point, New South Wales|Taren Point]]), and another sub-tidal reef downstream in [[Botany Bay]]. The reefs were intended to support reintroduced ''Ostrea angasi—''locally extinct in those waters since 1896—and also the now depleted Sydney Rock Oyster, ''Saccostrea glomerata.''<ref name=":20">{{Cite web |title=Restoring oyster reefs in Botany Bay |url=https://www.natureaustralia.org.au/what-we-do/our-priorities/oceans/ocean-stories/shellfish-reef-history-botany-bay/ |access-date=2024-02-10 |website=The Nature Conservancy Australia |language=en-AU}}</ref><ref name=":17">{{Cite news |last=Trembath |first=Murray |date=18 October 2023 |title=Oyster reefs to be built in Botany Bay and Georges River to boost fish populations and increase biodiversity |url=https://www.theleader.com.au/story/8387540/back-to-future-oyster-reefs-to-be-built-at-four-sites-in-botany-bay-and-georges-river/ |work=St George and Sutherland Shire Leader}}</ref> By April 2024, for the first time in well over a century, the Native or Flat oyster was present in the estuary.<ref>{{Cite news |date=2024-04-01 |title=Flat oysters return to Botany Bay after 100 years of local extinction |url=https://www.abc.net.au/news/2024-04-02/the-nature-conservancy-australian-flat-oysters-botany-bay/103634554 |access-date=2025-08-20 |work=ABC News |language=en-AU}}</ref> In December 2024, additional funding of the reefs was announced.<ref>{{Cite news |date=2024-12-06 |title=Mission to return flat oysters to Sydney gets millions to bring 'nature back into our suburbs' |url=https://www.abc.net.au/news/2024-12-06/funding-boosts-effort-to-bring-back-locally-extinct-flat-oyster/104689720 |access-date=2024-12-09 |work=ABC News |language=en-AU}}</ref> It is envisaged that the presence of the oyster reefs in the bay and estuary will increase both water quality and biodiversity, including an increase in the numbers of fish living there.<ref name=":173">{{Cite news |last=Trembath |first=Murray |date=18 October 2023 |title=Oyster reefs to be built in Botany Bay and Georges River to boost fish populations and increase biodiversity |url=https://www.theleader.com.au/story/8387540/back-to-future-oyster-reefs-to-be-built-at-four-sites-in-botany-bay-and-georges-river/ |work=[[St George and Sutherland Shire Leader]]}}</ref> Construction of reefs was proceeding during 2025.<ref>{{Cite web |title=Georges River Shellfish Restoration Revitalisation Project |url=https://www.natureaustralia.org.au/what-we-do/our-priorities/oceans/ocean-stories/georges-river-shellfish-reef-revitalisation/ |access-date=2025-08-20 |website=The Nature Conservancy Australia |language=en-AU}}</ref>
==References== {{Reflist}}
==Further reading== *{{cite web | title=Angasi oysters: Research Information Sheet | website= [[Department of Primary Industries (New South Wales)]] | date= 27 April 2016 | url=https://www.dpi.nsw.gov.au/fishing/aquaculture/publications/oysters/angasi-oysters}} * [https://archive.today/20121127003626/http://www.deh.gov.au/cgi-bin/species-bank/sbank-treatment.pl?id=69271 Australian Government Species Bank info page] (Archived version) *{{cite web | title=The Angasi oyster makes a comeback | website=ABC News ([[Australian Broadcasting Corporation]]) | date=10 April 2017 | url=https://www.abc.net.au/news/rural/2017-04-10/the-return-of-the-angasi-oyster/8426178|first=Nick |last=Bosly-Pask}}
{{Edible molluscs}} {{Taxonbar|from=Q7107731}} {{Authority control}}
[[Category:Ostrea]] [[Category:Commercial molluscs]] [[Category:Australian cuisine]] [[Category:Molluscs described in 1871]] [[Category:Bivalves of Australia]]