Plenty more fish in the sea? Environmental protections account for around 10 percent of fish stocks on coral reefs

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New research from the University of Sydney shows that international conservation efforts account for approximately 10 percent of fish stocks on coral reefs.  

The global study, published in Proceedings of the National Academy of Sciences, 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 US, UK, Kenya, France and Germany among others.   

Looking at fish survey data across nearly 2,600 tropical reef locations, the team developed a model that showed approximately 10 percent of fish biomass (the number and size of fish in an area) can be attributed to existing protections. 

Professor Cinner, Director of the Thriving Oceans Research Hub, said: “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. 

“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, this contribution appears quite modest and our study makes clear just how much room there is for improvement.”   

Across the world, coral reefs are under significant pressure from a wide range of human-made impacts including climate change, pollution and overfishing.  

Marine Protected Areas (MPAs) are sections of the ocean in which a government has placed restrictions on human activity and are a much-touted tool for preserving marine habitats. Currently, MPAs only cover a fraction (approximately 8 percent) of the world’s oceans, but this is set to expand rapidly in coming years.  

At the UN Biodiversity Conference in 2022, 196 countries adopted the Global Biodiversity Framework and committed to protecting 30 percent of the world’s terrestrial, freshwater, coastal and marine areas by 2030 – an initiative commonly referred to as 30x30. The authors hope their study will help maximise the benefits from this initiative.  

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

Dr Iain Caldwell, from the Wildlife Conservation Society, said: “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. 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 50 percent of coral reefs in their 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 coral reefs.    

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

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

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