2015-10-13 Planning & Organisation Agenda Attachment 1 to Item 7 Oyster Recruitment Assessment Report

Subtidal Oyster Recruitment

In general, 2–5 times fewer oysters recruited to tiles deployed at subtidal depths than
intertidally (Figure 5 & Figure 8). In contrast to the result for intertidal tiles, there was no
substantial difference in recruitment between surface orientations for plates deployed
subtidally, with a similar number of recruits on each surface (Figure 83). There was also no
significant difference in the average number of recruits among sites4; although recruitment
was very low at site LW2-S compared with that found at other sites (Figure 8). This is likely
due to a reduction in the suspended sediment loads at depth, and not being exposed at low
tide. There was an increase in the recruitment of other sessile species on subtidal tiles,
particularly barnacles, bryozoans and sponges.

Between February and May 2015, tiles deployed under a private jetty in Noosa Sound had a
much higher rate of oyster recruitment (mean ± SE of 2.8 ± 1.11 on horizontal and 5.0 ± 1.78
on vertical surfaces) than other sites throughout Weyba Creek and Lake Weyba (mean ± SE
of <2.0 ± 1.22 on horizontal and <0.8 ± 0.48 on vertical surfaces). There were a high number
of small polychaete worm tubes (Serpulids), and the bryozoan Schizoporella unicornis
covered more than 60% of the surface area of tiles deployed in Noosa Sound.




      Figure 8.    Average number (± SE) of oyster recruits (P. pestigris) on horizontal and vertical
                   surfaces deployed at subtidal sites


3
    PERMANOVA: orientation main effect pseudo-F1,30 = 2.48, p = 0.13
4
    PERMANOVA: site main effect, pseudo-F4,30 = 0.97, p = 0.44


Restoration of Noosa Estuary: An Assessment of Oyster Recruitment                                       11