A new study devised to “test the mettle” of global coral reef conservation has found that areas in which marine protection is at its most effective, fish numbers have risen by approximately 10%. It’s good news for those looking to reinforce the case for expanded global conservation efforts, but leaves vast room for improvement, lead researchers have said.

Taking a deep dive into fish survey data from across nearly 2,600 tropical reef locations, the global study – conducted by the University of Sydney and published in Proceedings of the National Academy of Sciences – found that approximately 10% of fish biomass can be attributed to existing marine protections.

The research was led by Professor Joshua Cinner from the School of Geosciences and lead analyst Dr Iain Caldwell from the Wildlife Conservation Society. The international research team also included scientists from the US, Kenya, France, and Germany.

Professor Cinner, who is also the director of the Thriving Oceans Research Hub, has suggested that the results of the research could have a positive impact on boosting fish stocks in areas of “vast over-fishing”, thus benefiting the coastal communities dependent on them.

“Millions of people depend on reef fish for their livelihoods and nutrition. However, overfishing is severely threatening the wellbeing of coastal communities right across the globe. Protection can help boost fish stocks and have flow-on benefits for people,” he said.

“Our study really tested the mettle of global coral reef conservation. On one hand, we found that conservation efforts have made a contribution to the amount of fish on global coral reefs, which is promising. But on the other hand, this contribution appears quite modest and our study makes clear just how much room there is for improvement.”

Across the globe, coral reefs are under significant pressure from a wide range of human-made impacts, including climate change, pollution, and overfishing. Global reefs are also currently subject to the fourth and most extensive mass bleaching event on record, driven by changing temperatures across the world’s ocean.

Marine Protected Areas (MPAs) have long been recognised as one of the most powerful tools in the toolbox for restoring ocean health. These MPAs are sections of the ocean in which a government has placed restrictions on human activity and issuing them with protections such as ‘no-take’ zones.

Currently, however, MPAs only cover a fraction of world’s oceans – approximated to be 8% – but it is hoped this will expand rapidly in coming years. The UN’s goal to protect and restore 30% of natural habitat on land and in water by 2030 will be a large contributor to this.

It was at the UN Biodiversity Conference in 2022 that 196 countries adopted the Global Biodiversity Framework and committed to protecting 30% of the world’s terrestrial, freshwater, coastal, and marine areas by 2030 – an initiative commonly referred to as 30×30. The authors hope this new study will help maximise the benefits from this initiative.

Professor Cinner, said: “Our modelling showed that we could get up to 28% more fish on coral reefs globally by increasing the coverage of fully protected reefs to 30% – but only is these reefs are chosen strategically.”

Vital to this will be the level of protection afforded to the ocean within these MPAs, with a greater onus on ‘no-take’ zones to enable the fuller restoration of ocean health. However, this isn’t the only means of restoring dwindling fish stocks.

“No-take zones are punching above their weight, especially when they are well complied with, but they aren’t the only way to increase fish populations,” said Dr Iain Caldwell from the Wildlife Conservation Society.

“While prohibiting fishing provides the biggest boost to fish biomass per unit area protected, other forms of fisheries management can also be effective and may be more amenable for people who depend on reef fish for their lives and livelihoods.”

More than half of the coral reefs observed in the study had no constraints on fishing at all, so the research team analysed what would happen if fishing restrictions – such as banning nets or spearguns – were put in place on all currently unmanaged reefs. 

Using their predictive model, the researchers found that global coral reef fish stocks would increase by a further 10.5% – essentially matching all conservation efforts to date.

“Fisheries restrictions aren’t as effective as no-take MPAs on a per area basis, but they tend to be less controversial with fishers, which means compliance can be better and they can be implemented at very large scales,” said Professor Cinner. 

“Sustaining coral reef fish populations will require using every tool in the toolbox.”

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