Comparing reef structure and mobile species assemblages at remnant and restored mussel reefs

Abstract The global loss of coastal habitats has reduced the availability of intact ecosystems to serve as reference systems for marine restoration and conservation, which poses a significant challenge for establishing ecological baselines to evaluate restoration and conservation success. In the Hauraki Gulf of New Zealand, extensive subtidal mussel reefs once played a critical role in maintaining the health of the system. However, due to large‐scale exploitation, degradation of the surrounding ecosystem, and a lack of protection, these reefs have failed to recover naturally, leaving only a few remnant subtidal reefs that are at risk of further exploitation. This study compared mussel reef structure and large mobile species assemblages at natural remnant and restored mussel reefs in the Hauraki Gulf to evaluate whether restored reefs resemble remnant reefs in physical structure and support similar mobile species communities. Both reef types exhibited similar structure, with higher mobile species diversity and abundance observed at remnant reefs, likely due to their proximity to complex rocky reef habitats, facilitating a wider range of ecological interactions. This study supports the use of remnant reefs to assist with the evaluation of mussel reef restoration and underscores the importance of conserving the remaining mussel reefs in the region.