What are Shellfish Reefs?

  • Banner S. glomerata intertidal clump

  • Banner_Subtidal reef.Photo: C.Gillies

  • Banner_Isognomon reef low tide. Photo IMMcLeod

Although shellfish reefs are among the most threatened marine habitats on earth little information is currently available on the ecology of shellfish reefs. Australian shellfish reefs are no different, with only a few species studied in detail (Saccostrea glomerata and Crassostrea gigas). Most Australian shellfish research focuses on describing life history, feeding, husbandry and disease in cultivated species (Crassostrea gigas, Ostrea angasi and Saccostrea glomerata) in support of shellfish aquaculture.

Shellfish reefs can be created by a single shellfish species (e.g. Saccostrea glomerata), or comprised of several reef-building species (for instance where Ostrea angasi co-occurs with Mytilus galloprovincialis or Pinna bicolor). Although shellfish reefs can vary in appearance depending on the dominant reef-forming species, they share a number of common attributes:

  • They provide habitat for other species by creating a hard substrate with high surface complexity, acting as attachment sites for sessile organisms and refuges for mobile organisms, supporting high levels of species diversity; 
  • They accrete dead shell material such that the reef grows in size and mass over time (except where restricted by tidal exposure or when harvested) with decay occurring at varying rates;
  • They provide food for other organisms, either when consumed directly or through the species assemblages they support.

Of the more than 2000 species of marine bivalves occurring within Australian nearshore waters, nine native and one introduced species are considered reef-building:

Crassostrea gigas_Ben Diggles

Crassostrea gigas
(Thunberg, 1793) Pacific oyster (introduced)

Primarily an intertidal species with a distribution from Tasmania, Victoria, South Australia and New South Wales, introduced from Japan in in 1947. Occurs intertidal to subtidal. Aquaculture fishery in Tasmania, South Australia and New South Wales.

Photo: Ian McLeod
Isognomon ephippium
 (Linnaeus, 1758) leaf oyster, rounded toothed pearl shell

Primarily an intertidal species with a distribution from New South Wales to Queensland and northern Western Australia. Occurs in association with mudflats, sandy bottoms and hard substrates. No recorded fishery or aquaculture within Australia.

Mytilus (edulis) galloprovincialis_Paul Hamer

Mytilus (edulis) galloprovincialis (Lamarck, 1819) bay mussel, blue mussel

An intertidal to subtidal species with a distribution from southwest Western Australia to northern New South Wales. Occurs on hard surfaces and sandy/muddy bottoms. A dredge fishery occurred in Victoria’s Port Phillip Bay from 1960’s to 1990’s. Aquaculture current in Tasmania, New South Wales, Victoria, South Australia and Western Australia (Australian Mussel Industry Association-http://www.australianmussels.com.au/portal/mussel-farm, last accessed 14/09/15).

Ostrea angasi_Chris Gillies
Ostrea angasi (Sowerby, 1871) native flat oyster, mud oyster, Port Lincoln oyster

Primarily a subtidal species with a southern distribution from New South Wales to Western Australia including Tasmania. Occurs from low intertidal areas to a depth of 30 meters. O. angasi reefs can also form mixed reefs in association with M. galloprovincialis and P. bicolour. Dredge fishery occurred from mid 1800’s to mid 1900’s in Tasmania, New South Wales, Victoria, South Australia and Western Australia. Aquaculture current or previously attempted in Tasmania, New South Wales, Victoria, South Australia and Western Australia.
Pinctada albina sugillata (Pearl oyster)_H.Alleway
Pinctada albina sugillata
(Reeve, 1857) pearl oyster

Occurs from Northern Territory to New South Wales and Upper Spencer Gulf, South Australia on hard surfaces in the lower intertidal as well as subtidal zones to depths of at least 50 meters. Most species of pearl oysters do not form reefs, however, P. albina sugillata forms reefs in Upper Spencer Gulf (Rutherford and Miller 2011) and possibly near Groote Eylandt, Northern Territory (Hynd 1960) and southern Queensland (B. Diggles pers. comm.). Can form mixed species reefs with Pinna bicolor in South Australia or S. glomerata in Queensland (plate 1G). Further research is needed to determine if other pearl oyster species such as P. maxima (gold lipped pearl oyster), P. margaritifera (black lipped pearl oyster) and P. fucata (akoya pearl oyster) may also form reefs.

Saccostrea cucullata Milky Oyster_IM McLeod
Saccostrea cucullata (Born, 1778) coral-rock or milky oyster

Primarily an intertidal species with a distribution extending from Queensland to Northern Territory and Western Australia. Occurs on hard surfaces, including mangroves and dead coral. Often forms mixed reefs with C. echinata becoming more dominant with increasing shelter. Previously formed an important local hand harvest fishery in central and southern Queensland. Current small-scale harvest and aquaculture trials 

S. glomerata clump 200x130

Saccostrea glomerata (Gould 1850) Sydney rock oyster

Primarily an intertidal species with a distribution extending from southern Queensland to northeast Victoria. Occurs in mid to low intertidal areas on hard substrates. Dredge and hand fishery on the east coast of Australia from early 1800’s (Kirby 2004), aquaculture in New South Wales, Queensland and Western Australia.

Trichomya hirsuta_Ben Diggles

Trichomya hirsuta
 (Lamarck 1819) hairy mussels

An intertidal and subtidal species with a distribution from South Australia east to Victoria, northern Tasmania, NSW and Queensland. Occurs on hard surfaces, often in bands below oysters. Trichomya hirstula is relatively tolerant of low dissolved oxygen (McIntyre 1959) but susceptible to mortality at salinities below 15 ppt. It is a prominent component of aboriginal middens along Australias east coast.

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