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

No change to seagrass composition or density was identified at any restoration sites. All
sites were dense (>70% cover) and long (>20 cm) eelgrass (Zostera capricorni) (except for
sites 13 and 16- see below). During the 12 month monitoring event, we identified small (leaf
height <1 cm), low coverage (<5%) growth of dugong grass Halophila ovalis inside the RAA
area at site 13, and some small patches within the rocky shore adjacent to site 16. This
seagrass was not present at the sites during installation (Table 1). The growth of seagrass at
these sites is likely due to lower runoff in Lake Weyba and Weyba Creek over the past yeah,
and especially in the past 6 months, and the stabilizing and baffling effects of the reefs on
surrounding sediments (especially at site 13). Further monitoring will be required on these
growing seagrasses.

Conclusions
In this report, we show that;
    1. Oyster restoration units have not moved from the RAA area, nor have they moved
         greater than 1 m within the RAA area.
    2. There has been significant spat settlement and oyster growth at all oyster reef
         restoration sites. Whilst this has not yet proliferated to coverage of invertebrates on
         the outside of the coir bags, or to the proper stabilisation of shell within the bags (i.e.
         cementing of the biogenic reef matrix), these oyster growth results are a positive sign
         for the likely success of the reefs in achieving these performance criteria in the near
         future.
    3. Whilst we did not identify any wilful damage to the oyster restoration units, we did
         identify that marker buoys were regularly removed from the oyster restoration sites,
         and there have been several instances of boat propeller and anchor strikes on the
         reefs. This was repaired where possible.
    4. There has been no significant change to the distribution, composition or quality of
         seagrass or mangroves around the oyster reef sites. Similarly, there has been no
         shoreline erosion at oyster reef sites.

Consequently, two of the four monitoring targets reported on here have been fully met, the
third relating to oyster and invertebrate growth is tracking very favorably with the criteria
likely to be met in the coming years, and the final relating to community usage may require
closer monitoring.

We identified some damage to the oyster reef units from boating activities (principally anchor
and prop damage) at many sites during the November 2018 monitoring event. We have
some evidence to suggest that the use of oyster reefs by fishers has increased over time,
and that some of the ecological benefits of the reefs might therefore be being offset by
fishing. The three reefs more distant from the main boating activities in Lake Weyba and
Weyba Creek (due to the combined effects of limits on access to hire boats, and difficulty of
access due to shallow waters) are the most intact oyster reefs, with no damage recorded in
either 2018 monitoring events. Whilst these reefs do not necessarily have the highest rates
of settlement (the exception being reef number 13, which has the highest average live oyster
density), their success might be the most guaranteed as they are less likely to be damaged
by the sorts of impacts occurring on reefs in the central stretch of the river.

References
BAGGETT, L. P., POWERS, S. P., BRUMBAUGH, R. D., COEN, L. D., DEANGELIS, B. M.,
     GREENE, J. K., HANCOCK, B. T., MORLOCK, S. M., ALLEN, B. L., BREITBURG,
     D. L., BUSHEK, D., GRABOWSKI, J. H., GRIZZLE, R. E., GROSHOLZ, E. D., LA
     PEYRE, M. K., LUCKENBACH, M. W., MCGRAW, K. A., PIEHLER, M. F., WESTBY,
     S. R. & ZU ERMGASSEN, P. S. E. 2015. Guidelines for evaluating performance of
     oyster habitat restoration. Restoration Ecology, 23, 737-745.
NEARMAP. 2018. NearMap photomaps [Online]. Available: http://www.nearmap.com.au/
     [Accessed November 2018].



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