Long-term monitoring describes unique fish communities across natural and artificial reef habitats in Indonesia.

Abstract

Artificial reefs (ARs) are commonly used as a tool in Indonesia to restore marine habitats and provide local communities with ecosystem services previously lost due to reef degradation, notably those related to fishing and tourism. Now, Indonesia has more reef restoration programmes than any other nation in the world. However, only 16% of reef restoration programmes in Indonesia are thought to monitor their reefs, and those that do often lack funding and capacity to conduct long-term (5 years or more) monitoring and to publish these results. We used Remote Underwater Video to monitor mobile assemblages over a 5 year period in Tianyar Bay, north Bali, Indonesia, in three habitat types: an artificial reef, degraded sand flat and natural coral reef to compare fish species richness and community structure between habitats over time. We found that (1) artificial reefs can support similar communities to coral reefs even after a short time (~ 1–3 years after deployment), (2) coral and artificial reef fish communities and trophic groups do not fully converge over a 5 year period, with the AR consistently supporting greater populations of predatory fish and the coral reef supporting greater populations of planktivorous and herbivorous fish, (3) both communities on the coral reef and artificial reef responded in a similar manner to localised environmental and ecological changes (e.g. recruitment, predator-prey interaction, environmental factors, unusual weather patterns) and/or external factors (such as fishing), and (4) the 5 year dataset allows us to draw different conclusions to what we would have after a 3 year dataset, much more commonly associated with research funding timescales. Ultimately, longer-term data sets are needed to make stronger conclusions on how artificial reefs can support similar communities to natural reefs. Given the continued, large-scale deployment of ARs as a habitat enhancement tool, collecting long-term data on their ecology should be prioritised if we are to better understand their effectiveness and full restoration potential.