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

                                                             Ecological Service Professionals
                                                                                 Sustainable Science Solutions

Assessing the Presence of Smothered Oyster Beds
To assess for the presence of hard substrate (rock, rubble or shell grit) beneath soft
sediment, we probed bare substrate in at least 5 points at each of the 16 sites to determine
the extent of buried oyster shell if present and at several other locations throughout the
estuary where oyster rubble was detected on the camera or where oysters were found along
the shoreline. Probing of the sediment was completed using a narrow 2.4 m (1 cm wide)
Kevlar probe to determine whether hard substrate or shell/rubble layer could be located
below the sediment surface. The depth of sediment overlying these layers was recorded
where hard surfaces were detected (Table Appendix A).
Due to time constraints, our survey was limited to areas:
   1) along the main Noosa River channel from Hays Island to 715 m upstream of the
      Tewantin Ferry;
   2) areas known to have rocks based on boating charts in Lake Weyba; and
   3) along the main channel of Weyba Creek.

In situ Water Quality
We also assessed the water quality at each of the sites identified in the RAA along the
estuary using a YSI ProDSS multi-parameter water quality sonde. The probe was calibrated
prior to going into the field and the following parameters were assessed: temperature (°C);
salinity (PSU); conductivity (µS/cm); dissolved oxygen (mg/L & % saturation); turbidity (NTU);
pH & depth (m).

Limitations
These preliminary assessments were qualitative in nature and additional work would be
required to assess the density of live oysters and to confirm the full extent of historical oyster
beds and the depth of oyster shell or rubble present along the estuary that is currently buried
under fine sediment. A targeted assessment, including sediment coring, could be used to
identify the density of historical oyster shell that remains in the system (i.e. that was not
removed for lime and road base) in areas not assessed in this report. Carbon dating could
be used to determine the age of oysters below the sediment surface which could be used to
recreate a historical account of change in the sediment budget of the Noosa Estuary,
although this information would be useful for the long-term restoration of the Noosa Estuary,
it is not critical to inform the proposed restoration project, and is considered excessive for the
scale of proposed restoration works. The methods provide in this report present an adequate
and conservative determination of the minimum surface area and location of historical oyster
habitat in the Noosa Estuary.

Historical Account of Oysters in Noosa River Estuary
Oysters were a food source for the Kabi Kabi traditional owners, who provide the first record
of the Noosa Estuary. Historical newspaper accounts of the density of oysters in the Noosa
Estuary indicate that there were plentiful oysters with remnants found in middens around
Tewantin to a depth of approximately 4 m, evidence of a substantial and sustained source of
food.
“Oysters are very plentiful, but are, I am told, gradually being killed by the pearl-bearing
species, which here are of no commercial value. The banks of the river at Tewantin, for a
depth of 12 or 13 feet, are entirely composed of oyster shells, which have no doubt been
accumulated by the blacks, charcoal and stone tomahawks having been found 6ft below the
surface.” Australian Town and Country Journal, 29 Apr 1882 (cited in Thurstan 2015).


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