2016-12-12 General Committee - Attachments 1, 2, 3 to Item 10 - Oyster Restoration Project

                                                             Ecological Service Professionals
                                                                                 Sustainable Science Solutions

Several dead oyster shell beds were recorded at or below the sediment surface. The lack of
vertical height above the sediment, suitable surface orientations (lack of overhanging
surfaces) and high mobility/accumulation of fine sediment is likely to contribute to the low
numbers of live oysters currently growing in these areas.
Living oyster aggregations were found in the Noosa Estuary only where hard surfaces
protruded from the sediment or on hard surfaces where fine sediment could not settle (i.e. on
vertical surfaces or those in the intertidal where wave action removes fine sediment).
One living leaf oyster (a large flat oyster species which can provide substrate for rock
oysters) bed of 4050m2 was recorded in Weyba Creek.
Based on field observations, a suitable way to assist restoration of habitat is to reintroduce
dead shell (a preferred settlement surface) at a suitable vertical height on the shore (above
LAT) and with sufficient vertical relief to mimic natural oyster reefs (i.e. >0.5 m). Abundant
oyster shell was historically used by oyster cultivators to stabilise banks and improve the
productivity of oyster harvesting areas. Therefore, creating restoration structures with
suitable overhanging surfaces, at a sufficient height on the shore (above LAT as this is where
most oysters currently grow), with sufficient vertical height above the surface (i.e. >0.5m) and
stabilisation of sediment has a high likelihood of success.
The proposed total Resource Allocation Area for oyster restoration is 1440 m2, which
combined with the existing leaf oyster bed (4050 m2) and oyster aggregations on rock rubble
(16,597 m2), represents <54% of areas likely to contain oyster beds or reefs in the Noosa
estuary based on 1% of the accommodation space (area with ambient water quality
conditions suitable for oyster growth) within historical oyster lease areas.
We understand that all restoration is to be completed on bare sediment. Based on an
assessment of the likely historical extent, location within the estuary, current ambient
environmental conditions, presence of oyster spat and the presence of adult oysters on
nearby hard substrate, the proposed restoration effort would not represent substitution of
bare sand habitat. Instead it would restore a natural habitat where oysters were once
abundant (but now often buried under sand and silt, or likely to occur but habitat was
removed through dredging).



Background
It is estimated that globally, the biogenic reef habitat (i.e. habitat produced by living
organisms) formed by oysters in estuaries has declined by up to 85% of historical extent and
is functionally extinct in many estuaries, particularly along the east coast of Australia (Beck et
al. 2011). Biogenic oyster habitat forms when oysters aggregate on soft sediment or hard
surfaces, in the lower intertidal and subtidal areas of estuaries. Biogenic oyster habitats are
classified into three types according to Beck et al. (2009):
1) Oyster reefs are formed where oysters are the dominant structural component, and can
provide up to 0.5 m of vertical height above the surrounding sediment surface.
2) Oyster beds are formed where oysters aggregate in high densities, are the dominant
structural component, but provide less than 0.5 m in vertical height
3) Oyster aggregations grow on underlying hard structures (i.e. bedrock, rocky rubble, and
mangrove pneumatophores).




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