Mr Juan Esquivel-Muelbert1
1Macquarie University, Sydney, Australia
Predation is a key process limiting recruitment and habitat formation by reef-building shellfish. Restoration projects may protect recruits from predators by caging/netting recruitment substrates or by providing recruitment substrates that are topographically complex. Biodegradable Ecosystem Engineering Elements (BESE) are complex 3D structures made out of potato starch, that are designed to provide a large surface area of protected habitat for shellfish recruitment. We assessed whether BESE units support the same pattern of oyster recruitment enhancement across an environmental gradient of inundation as caging concrete substrate. Uncaged and caged concrete blocks, and BESE units were deployed at three tidal elevations (mid and low intertidal and subtidal) of three sites. One year following deployment, oyster recruitment to uncaged concrete blocks was low, at all sites and tidal elevations. Cages bolstered oyster recruitment at all elevations, with this enhancement greatest at the mid intertidal elevation. Contrary to expectations, recruitment to BESE did not support similar patterns of recruitment enhancement as caged concrete blocks. While recruitment to mid and low intertidal BESE was high, recruitment to the subtidal was more commensurate with the uncaged than the caged blocks. Sampling of fish revealed that known predators of oysters such as Girella tricuspidata were able to penetrate the 3 cm BESE mesh and live within the matrix. In summary, while BESE units provided suitable substrate for oyster settlement, they did not appear to successfully mitigate predation in the subtidal. Our results highlight the need to understand predator assemblages before designing restoration projects.
Presentation Slides – Juan Esquivel-Muelbert
Biography:
Juan Esquivel-Muelbert is an aquatic ecologist with special interest in using evidence-based information to improve habitat restoration planning and practice. He is a current PhD candidate at Macquarie University, where he is developing a research project focused on understanding the effects of biotic and abiotic factors on oyster reef formation and maintenance.
