Enclosure 6 - ESP Letter

                                                                 Ecological Service Professionals
                                                                                     Sustainable Science Solutions

By the late 1930s, the oyster fishery harvest in Southeast Queensland, including Noosa
Estuary, went into depression (Smith 1981). Ultimately it is thought the natural oyster banks
were unable to recover due to both the removal of live oysters and dead shell from the
Noosa system (Monks 2000, cited in Thurstan 2015; Smith 1985). Declining water quality
resulting in recruitment failure of oyster spat and disease has also been implicated in the
general decline of oyster banks in Moreton Bay (Diggles 2013).




    Figure 6     Historical photo showing the large size of bagged oysters in 1908 (Smith 1981).



Identifying Current Oyster Accommodation Space
The accommodation space represents the area in an estuary with environmental conditions
suitable for growth of oysters (Volety 2013). Oysters grow from the intertidal to depths of at
least 20 metres and this is where much of the hand gathering or dredging of oysters has
historically occurred (Nell 2001). However, it is thought that due to changes in ambient
conditions and a variety of external factors, rock oysters in Southern Queensland are
typically found only in the intertidal zone and have been functionally lost from subtidal
habitats (Diggles 2013). Conditions suitable for optimal oyster growth are summarised in
Table 2, from Nell & Halliday (1988), Halliday (1995) and Rubio (2007).

    Table 2      Temperature and salinity for optimum growth and tolerance limit

Parameter                                 Units         Life History Stage

                                                        Larvae               Spat             Adult

Temperature optimum growth                °C            24-26                14-28            18-26

Temperature tolerance limit               °C            unknown              11-30            11-30

Salinity optimum growth                   ppt           23-39                20-40            25-35

Salinity tolerance limit                  ppt           15-39                0-40             0-50



Adult rock oysters are able to close their valve for several days if salinity is less than 15 ppt,
although prolonged periods of low salinity can cause death (Nell & Halliday 1988; Halliday
1995).




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