Subtidal oysters

Long description

Subtidal oysters growing on unconsolidated substrates, and unconsolidated boulders and gravel (i.e. cobbles, pebbles etc. including rubble) and potentially also on sands and muds. Historically, subtidal oyster reefs of the rock oyster Saccostrea glomerata were reported as deep as eight metres.

Being filter feeders, oysters are vulnerable to changes in water quality. Surrounding catchment landuse can impact on them, and they become vulnerable to diseases, biotoxins and bacterial contamination.

The likely ecosystem-forming species, their current status and reasons for their decline in Australia are well documented[1].

Other non-commercial reef-forming oysters include the slipper oyster Isognomon ephippium.

Special values

Valued for aquaculture for edible oysters (including their spat, i.e. larval juveniles ready to settle on consolidated substrate) and pearl oysters. Historically an important dredge and hand fishery and aquaculture from southern Queensland to Victoria.

Evidence of indigenous use is present in middens (S. glomerata, I. Ephippium).

Other ecosystem services include water quality treatment, fish production, blue carbon and coastal protection. Artificial shellfish reefs are being advocated as a water quality treatment system, as they filter suspended sediment and plankton from the water column (for a list of ecosystem services see Treatment systems-Shellfish reefs and type 118).

Shellfish ecosystems are listed in the Ramsar convention as an ecosystem type[1].

Diagnostic attributes

Inundation 'Subtidal'

Structural macrobiota 'Mollusc – oysters'

Consolidation - 'Unconsolidated' 'Intermediate' or 'Unknown'

Qualifiers

Although unmapped, the Naturalness qualifier is relevant to the Consolidation attribute as subtidal oyster ecosystems can include introduced structures (e.g. longlines, panels and cages for pearl oysters, and racks and trays for rock oysters, and shell and cages for artificial shellfish reefs). Modified Naturalness of Structural macrobiota applies to introduced species e.g. Japanese Akoya pearl oysters and Pinctada maxima.

There are biosecurity issues associated with introduced species. See Comments below regarding predators and diseases.

Distribution

In Queensland, Australia, and Worldwide, , oyster reefs are reduced to a fraction of their previous extent through overfishing, destructive fishing practices such as dredging, water pollution and disease[2].

The following relates to distribution of this ecosystem type within the Central Queensland mapping area:

• No substantial subtidal oyster reefs are mapped in Central Queensland, although historically the area was targeted as a shellfish fishery, predominantly Port Curtis and the Great Sandy Strait. The extent and nature of natural oyster reefs in Queensland is poorly known[1].
• The Great Sandy Strait is a Ramsar site, with Ramsar listing shellfish ecosystems as a type.

Comments

This ecosystem type includes commercial species targeted for aquaculture, regulated by Fisheries Queensland for which guidelines are available. Predators include mudworm Polydora, oyster drill gastropod molluscs and QX disease, caused by the microscopic parasite Martieilia sydneyi. Gillies[1] highlight the need for work on the classification, mapping and management of shellfish ecosystems, and better quantification of their ecosystem services.

Additional Information

Shellfish reefs (treatment systems) - WetlandInfo

Shellfish Reef Restoration Network

Shellfish Reef Restoration in Pumicestone Passage - Restore Pumicestone Passage

Rock oyster aquaculture - Queensland Government

References

1. ^ a b c d Gillies, CL, McLeod, IM, Alleway, HK, Cook, P, Crawford, C, Creighton, C, Diggles, B, Ford, J, Hamer, P, Heller-Wagner, G, Lebrault, E, Le Port, A, Russell, K, Sheaves, M & Warnock, B (14 February 2018), 'Australian shellfish ecosystems: Past distribution, current status and future direction', PLOS ONE. [online], vol. 13, no. 2, p. e0190914, ed. L D Coen. Available at: https://dx.plos.org/10.1371/journal.pone.0190914 [Accessed 25 March 2019].
2. ^ Saville-Kent, W (1893), The Great Barrier Reef of Australia: Its Products and Potentialities, John Currey, Melbourne, Australia.

Last updated: 11 July 2019