Subtidal oysters on consolidated substrate

Long description:

Subtidal oysters growing on consolidated substrates, forming shellfish reefs. The current nature and extent of shellfish reefs on consolidated substrates is poorly understood. Historically, subtidal oyster reefs of the rock oyster Saccostrea glomerata were reported as deep as 8 metres. The likely ecosystem-forming species, their current status and reasons for their decline are documented[1]. Other non-commercial reef-forming oysters include the slipper oyster Isognomon ephippium that also occurs in intertidal and unconsolidated substrates.

Being filter feeders, oysters are vulnerable to changes in water quality and surrounding catchment land use can impact on them, making them vulnerable to diseases, biotoxins and bacterial contamination.

Special values:

Valued for aquaculture for edible oysters (including their spat, i.e. larval juveniles ready to settle on consolidated substrate) and pearl oysters. Evidence of indigenous use is present in middens (S. glomerata, I. Ephippium). Historically an important dredge and hand fishery and aquaculture from southern Queensland to Victoria. Other ecosystem services include water quality treatment, fish production, blue carbon and coastal protection. Shellfish ecosystems are listed in the Ramsar convention as an ecosystem type[1] and Queensland has four intertidal to subtidal Ramsar sites (Moreton Bay, Great Sandy Strait, Shoalwater and Corio Bay and Bowling Green Bay).

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.

Oysters also grow subtidally on unconsolidated substrates (see 64).

Diagnostic attributes:

Inundation 'Subtidal'

Structural macrobiota 'Molluscs' 'Oysters'

Consolidation 'Consolidated or Intermediate'.

Qualifiers:

Any artificial shellfish reef or oyster aquaculture that introduces a consolidated structure into a previously unconsolidated ecosystem modifies its Naturalness, and is a qualifier of the Consolidation attribute. Modified consolidation applies to artificial structures (e.g. longlines, panels and cages for pearl oysters, and racks and trays for rock oysters, and the shells and cages for artificial shellfish reefs). Modified Structural macrobiota attribute relates to introduced aquaculture species, Japanese Akoya pearl oysters and Pinctada maxima were also trialled for a period in the Great Sandy Strait.

Distribution:

In Queensland, Australia, and Worldwide, oyster reefs have been substantially reduced in extent through water pollution and disease, overfishing and destructive fishing practices such as dredging.

Artificial shellfish reefs are being created on the Sunshine Coast and in the Pumicestone Passage, in an effort to restore the previous distribution of shellfish reef ecosystems (see Additional Information).

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

• Historically (1860 to 1920) Central Queensland was targeted as an extractive shellfish fishery, where oysters predominantly from Port Curtis and the Great Sandy Strait were taken down to Moreton Bay for fattening and sale[1].

Comments:

This ecosystem type includes commercial species targeted for aquaculture, regulated by Fisheries Queensland for which guidelines are available. Work is needed on the classification, mapping and management of shellfish ecosystems, and better quantification of their ecosystem services[1].

Other relevant attributes include Substrate composition as structures for aquaculture include wooden and metal frames, racks, cages and longlines. Subtidal oyster ecosystems have been impacted on by poor water quality and catchment runoff, a combination of factors related to Water clarity, Energy source (riverine) and Freshwater source (riverine) and Volume, and Sediment texture (suspended sediment and deposited). Poor water quality can lead to infestation by predators and disease. Predators include mudworm Polydora, oyster drill gastropod molluscs and QX disease, caused by the microscopic parasite Martieilia sydneyi .

Additional Information

Shellfish reef 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].

Last updated: 22 July 2019