Protecting 5% More Of The Ocean Can Increase Fisheries Yield By 20%

new study, published in the Proceedings of the National Academy of Sciences, found that protecting an additional 5% of the ocean can increase future fish catch by 20% or more. Growing up in a fishing community in the Philippines, lead researcher Dr. Reniel Cabral believes that marine protected areas (MPAs) can benefit both conservation and fisheries goals simultaneously. In the past, MPAs have been used as conservation tools, however a focus on fisheries may provide a necessary incentive for many coastal nations to adopt or expand them. 

“We are curious if we design MPAs to increase fisheries productivity on a global scale, how much food can we generate, and how expensive will it be?” says Dr. Cabral, who hopes to see 30% of the world’s oceans protected by 2030; a widespread conservation goal. Currently only 2.5% of the ocean is fully protected, however Dr. Cabral anticipates that the research will provide a scientific basis for nations to view protected areas as investments into the future success of their fisheries.

The study entitled “A global network of marine protected areas for food” looked at MPA siting and area coverage using fisheries data for over 1,300 commercially-important fish species to determine how much fish biomass could be available for the fishing industry if more of the ocean was protected. Building on years of previous research, the research team modeled protection networks to predict fisheries success. They found, unsurprisingly, that expansion of MPAs will have the greatest impact in areas where overfishing is occurring, which is often in the developing world where fisheries management resources are less robust.

As the protected area increases, so does fisheries success, however according to the models once 47% of the ocean is protected, expanding marine protected areas further will not improve fisheries and will in fact hinder total catch. “While you can close up to 47% of the ocean, most of the benefits [to fisheries catch] you can achieve by protecting a smaller percent of the ocean,” says Dr. Cabral. The majority of the impact occurs when 5-10% more of the ocean is protected, according to the research.

When MPAs are strategically implemented in areas where overfishing or poor management are occurring, the models show that fish populations will be able to recover and leave the protected areas to re-stock unprotected areas. This phenomenon is known as spillover effect. The fish in MPAs are able to grow bigger and produce a higher number of more hearty offspring. The study found that protecting 5% more of the ocean would result in nine to twelve million more metric tons of fish catch annually. The modeling was carried out by examining areas of 55 kilometers by 55 kilometers. By calculating the species biomass in each area, taking into account fish biology and movements, the team was able to predict how much fish catch would be possible if the area was fully protected. They then subtracted the amount of fish already being caught in those areas to provide an estimate of how much fish catch would increase with greater protections.

Protecting swaths of the ocean has long been championed by conservationists as one of the best ways to ensure ecosystems remain intact and productive, however the expansion of MPAs is often viewed as a threat to fisheries stakeholders who may see protections as a loss of fishing grounds and a loss of income. Yet the study shows that by protecting these spaces now, fisheries stakeholders will benefit from greater returns in the long run.