Comparing Effectiveness of Aquatic Reserves in the Hawkesbury shelf bioregion, NSW

The Hawkesbury shelf is the only coastal bioregion in New South Wales (NSW) without a Marine Park. The NSW government established 12 small aquatic reserves in the Sydney area (part of the Hawkesbury shelf) over a decade ago,... [ view full abstract ]

The Hawkesbury shelf is the only coastal bioregion in New South Wales (NSW) without a Marine Park. The NSW government established 12 small aquatic reserves in the Sydney area (part of the Hawkesbury shelf) over a decade ago, each with a different policy and aim to protect specific habitat types and associated marine life. Despite protection these aquatic reserves and surrounding areas are threatened by urbanization, pollution, over-fishing and climate change, to name a few. Thus, the NSW government is currently considering the implementation of a Marine Park in this bioregion, implying a higher level of protection, however there is little information available to support the government’s decision.
The aim of this study is to investigate the effectiveness of aquatic reserves in the Hawkesbury shelf bioregion. We investigated the biodiversity and abundance of fish and mobile invertebrate assemblages across aquatic reserves with different protection levels and compared these to unprotected sites. We used Reef Life Survey (RLS) data collected in late summer of 2015 on shallow reefs (3 – 10 m) in 18 sites. The RLS method uses underwater visual census (UVC) along 50 m x 10 m transects, where fish are counted and size classed. Along the same transect, RLS method also uses UVC within a 1m range of the transect tape to quantify abundance of benthic mobile macro-invertebrates and size and abundance of cryptic fish.
The differences between sites and protection levels on community assemblage and composition were analysed using a Permutational Analyses of Variance in PRIMER. We found significantly higher diversity and abundance inside aquatic reserves with the highest level of protection where no spear or line-fishing is allowed. The other reserves, with lower levels of protection and lack of enforcement, however, did not differ significantly in diversity or abundance compared to sites outside reserves. We conclude that only high levels of protection and enforcement have significant results on fish and benthic assemblages and are effective forms of protection. These results can inform the Hawkesbury shelf bioregion spatial assessment, and will help identify sites of high ecological importance.