2019-01-14 General Committee Agenda - Attachment 3 to Item 2 - Monitoring of Noosa River Oyster Reefs Nov 2018

Executive summary
  1) Background & Rationale
     The principle objective of the Noosa Oyster Reef Restoration Project is to restore
     ecologically-functioning oyster reefs to the Noosa River Estuary. Reef units were
     installed in November 2017 to begin the restoration. An annual monitoring is part of
     the approval (OPW17/0016) that needs to report on: a) reef unit stability; b) oyster
     spat recruitment processes; c) lack of negative community usage; and d) impact on
     marine plants and shoreline erosion. This report addresses these requirements,
     reporting on the findings of two mandated monitoring events (May 2018, Nov. 2018)
     done by USC. The methods used were precisely those prescribed in the approved
     monitoring schedule, with no modifications.

  2) Stability and Position
     The reef units can be considered stable. The mean recorded change in position over
     12 months was 0.16 m (+/- 0.12 m SD). All oyster reef restoration units moved less
     than 0.65 m over one year. No reef unit moved from the designated resource
     allocation areas at any site. No reef unit was physically displaced from its anchor
     points in the sediment or removed otherwise.

  3) Recruitment
     Substantial spat fall and oyster growth was found in both monitoring events. In May
     2018, an average spat fall of 387.5 oysters/m2 (+/- 537.7 oysters/m2 SD) was
     recorded, and in November 2018 it was 306.1 oysters/m2 (+/- 575.1 oysters/m2 SD).
     There was a significant increase in the size of newly recruited oysters on the reefs.
     Here oysters increased in size from 14.3 mm (+/- 6.5 mm SD) in May 2018, to 19.1
     mm (+/- 8.9 mm SD) in November 2018. The favourable spat fall and oyster growth
     are an encouraging bellwether for the reefs to develop into biologically stable
     systems over the coming years.

  4) Interaction with Public
     There were signs of damage to a few reef units most likely caused by boat propellers
     and anchors, evident during the November 2018 monitoring event. We repaired
     these units where possible. Limited data suggest that the use of the oyster reefs by
     recreational fishers possibly appears to have increased over time. We suggest that
     closer monitoring of this aspect may be useful in coming years.

  5) Marine Plants & Shoreline Erosion
     Whilst there was some change to the edges of seagrass beds, there were no
     significant changes to the distribution, cover, or species composition of existing
     seagrass beds or mangroves forests within 50 m of each reefs. We found no
     shoreline erosion in the vicinity of the reef units. At two sites in Lake Weyba and
     Weyba Creek dugong grass Halophila ovalis was found near reef sites where it was
     not recorded at the time of reef placement.

  6) Conclusions
     Overall, the results of the 2018 monitoring of the Noosa oyster reefs are encouraging
     and positive. Two of the targets have been fully met (reef unit stability, no impact on
     plants and shorelines). The target of oyster and other invertebrate growth is tracking
     very favourably. The observation of reef unit damage from anchoring needs
     consideration of closer monitoring and possibly targeted education / information may
     be considered for this issue. The next scheduled monitoring event is mandated for
     May 2019.




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