Scientist says marine sanctuaries fall short of expectations

By Pacific Island Times News Staff

Fish stocks within marine sanctuaries do not repopulate as much as commonly believed, a fishery scientist said, citing a study suggesting that protected open-ocean areas do not meet expectations.

Ray Hilborn, a professor with the University of Washington, examined the limited data available from within existing monument closures, new information from recent reopenings and economic performance of U.S. longline vessels before and after closures.

He delivered a presentation at the Scientific and Statistical Committee’s 158th meeting in Honolulu, where the scientific panel weighed the pros and cons of restoring commercial fishing in U.S. Pacific marine national monuments in response to President Trump’s April directive.

The target areas are the Marianas Trench, Papahānaumokuākea and Rose Atoll national monuments.

Hilborn, a member of the committee under the Western Pacific Regional Fishery Management Council, presented an analysis that compared widely promoted claims that large marine protected areas increase biodiversity, create healthier ecosystems and support sustainable fisheries with empirical evidence from the Pacific.

He cited a 2023 study on the Phoenix Islands Protected Area, which showed that modeled increases in tuna abundance through spillover “were modest (on the order of a few percent) and may not translate into large fishery gains.”

The 408,250-sqkm Phoenix sanctuary is a UNESCO World Heritage Site located about halfway between Hawai‘i and Fiji. It was once the world’s largest marine protected area.

The study, published by Dr. John Hampton of the Pacific Community, found that the Phoenix Island Protected Area “does not have discernible conservation benefits for Pacific skipjack and bigeye tuna, two of the most important tropical tuna species to U.S. fisheries.”

At the committee meeting, Hilborn told the panel that in U.S. monument waters, where historical fishing pressure was relatively low, large ecological responses to closure are not expected.

He said recent studies have found no measurable increase in tuna biomass density inside open-ocean protected areas and, in some cases, substantial reductions in bigeye catch-per-unit-of-effort linked to the loss of historically productive grounds.

Marine monuments are established to protect aquatic ecosystems, preserve biodiversity and provide habitats for natural resources to thrive.

Hilborn, however, argued that closures of marine national monuments create an illusion of “protection” while leaving non-fishing threats ignored.

Hilborn told the committee that well-regulated U.S. fisheries under the Magnuson–Stevens Act are unlikely to pose an abatable threat to pelagic stocks and that any threat can be addressed by creating large marine protected areas alone.

He said the Magnuson–Stevens Act's management frameworks and the Western and Central Pacific Fisheries Commission already provide tools to achieve conservation goals while considering human and community impacts.

Eric Kingma, executive director of the Hawaii Longline Association, said existing monument area closures “exclude U.S. vessels from U.S. waters and leave us very constrained in where we can fish.”

Citing declining bigeye catch rates, Kingma emphasized that “we need to be able to find and follow the fish – that’s the most important part.”

“We’re not looking for more fish, but to have the opportunity to fish more efficiently away from competitors,” Kingma said. 

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