Factors Influencing Recruitment of Sydney Rock Oysters (Saccostrea Glomerata) in NSW, Australia

The worldwide degradation of oyster reefs, and a growing appreciation of their considerable ecological and socio-economic worth, has prompted the development of strategies to recover their habitat. In environments with larval supply, recruitment can be a good indicator of restoration potential. We implemented a field experiment in five estuaries of New South Wales, Australia, spanning eight degrees of latitude, to determine how abiotic and biotic factors interact to influence Saccostrea glomerata recruitment. In each estuary, we deployed concrete substrate for oyster settlement at three sites of varying distance from the river mouth, each proximate to extant oyster populations. Substrate was deployed across a tidal elevation gradient spanning the mid intertidal to shallow subtidal and was caged, uncaged, or partially caged, so as to assess the importance of predation to recruitment. The number of recruits varied among estuaries along the latitudinal gradient, decreasing with increasing average temperature, dissolved oxygen concentration, and turbidity. Recruit density also varied within sites, initially increasing with tidal elevation and consistently increasing with caging. Consequently, recruitment of S. glomerata appeared limited both by environmental factors and predation. Hence, predator exclusion and habitat suitability modelling are needed to maximise the probability of successful oyster reef restoration.