Effectiveness of a deep water fully protected marine reserve five years after establishment

Mesophotic coral reef habitats and their associated fish assemblages are underrepresented in marine protected areas world-wide. The effectiveness of a mesophotic, fully-protected marine sanctuary in the Ningaloo Coast World Heritage Area was assessed 5 years after establishment by surveying fish assemblages. Overall diversity and biomass of fish assemblages in the sanctuary was maintained between 2019/21 and 2024, and both these parameters were significantly higher in the fully-protected area than in the fished area. For fishes targeted by fishing, species richness and abundance were also significantly higher in the fully-protected zone relative to the area open to fishing. The abundance of sharks increased significantly in 2024 but did not differ between fully-protected and fished areas. Results suggest the success of sanctuary since it was established. Further improvement in the parameters measured are likely, as marine sanctuaries usually take many years to respond to the removal of fishing mortality. However, the Point Cloates area is remote, and levels of recreational fishing effort there are thought to have been lower, relative to other parts of the Ningaloo coast. Commercial fishing in the area ceased in the 1970s. Thus, recovery to an unfished state may occur more rapidly, especially as the area is adjacent to another large fully-protected sanctuary established in 2005 that reaches the shoreline. Given few mesophotic habitats in the area are fully protected, the Point Cloates sanctuary is important. The precautionary principle guides the need to protect what are currently remote areas but are unlikely to always be so.