Why Marine Protected Areas Need More Than Fisheries Data

Meeting with NOAA in 2024.  Conservation voices have a fraction the influence of fisheries voices in managing US oceans.

Last year, my colleagues Kirsten Grorud-Colvert, Jenna Sullivan-Stack, Steven Mana’oakamai Johnson, and I published a short piece in Nature calling on philanthropy and NGOs to "Study protected waters newly opened up to fishing." I publish the short article below in its entirety:

In April, the United States opened up one million square kilometres of the Pacific Islands Heritage Marine National Monument to commercial fishing. Before then, for a decade, the region had been a marine protected area — in which all fishing was prohibited. Courts reclosed the area this August as part of an ongoing legal battle. Other protected areas, including the Papahānaumokuākea, Rose Atoll and Northeast Canyons and Seamounts marine national monuments, are under review (see go.nature.com/44Zambm).

We urge research and philanthropic organizations to support scientific monitoring of these waters, to assess the effects on marine life and on communities in American Samoa, which is nearby. Some argue that allowing fishing would benefit the tuna-canning industry in American Samoa, providing socio-economic and public-health benefits (see go.nature.com/3uf25ti).

Lessons learnt — as well as the international policy goal of conserving 30% of the ocean (J. Lubchenco et al. Nature 588, 30–32; 2020) — should be key to future decision-making about marine protected areas in the United States and globally.

Publishing these correspondence pieces are challenging. Scientists are rarely known for being succinct. We packed a lot of ideas in a very short word limit, trying to point out that with these wild swings in policy happening, we need to study the biological and social outcomes. We directed our letter at philanthropy and NGOs, because without them, the agenda would be set by fisheries.

Well, guess what happened?  This week the Western Pacific Regional Fishery Management Council sent out an email describing an analysis by the Pacific Islands Fisheries Science Center (PIFSC) examining whether long-term closures around Johnston Atoll produced “spillover” benefits and whether a brief 2025 reopening changed catch rates for the Hawai‘i longline fishery. 

Johnston Atoll Spillover and Reopening Effects Evaluation
SSC members will discuss a new Pacific Islands Fisheries Science Center analysis examining whether long-term fishing closures around Johnston Atoll produced measurable spillover benefits to nearby fishing grounds. The committee will also review whether the brief 2025 reopening of portions of the marine national monument resulted in immediate catch-rate changes for the Hawai‘i deep-set longline fishery.

Using 20 years of fishery logbook data and species-specific statistical models, researchers found that the effects varied by species and by spatial scale, highlighting the complexity of evaluating large marine protected areas and highly migratory pelagic species.

The discussion is expected to provide insight into how large-scale ocean closures and reopening scenarios may influence fisheries, catch rates and future management strategies in the Pacific.

The PIFSC analysis asks whether MPAs improve catch rates and benefit fisheries. These are reasonable questions—but it's important to remember they are not the primary purpose of MPAs. Protected areas are designed to conserve biodiversity, rebuild ecosystems, protect cultural resources, and enhance resilience. Many of these outcomes are not captured in fisheries logbooks or short-term catch trends.

When fisheries performance becomes the main metric, success is subtly redefined. An MPA that does not increase adjacent catch may be seen as ineffective, even if it is ecologically thriving. Conversely, reopening may appear beneficial if catch rates rise, even if ecosystems are degraded over time. This framing risks skewing both science and policy.

With that said, this fisheries study showed that there were some really importance fisheries benefits!  The analysis looked at the spillover effects (analyzing the catch data outside the monument) and reopening effects (analyzing the catch data inside the monument when it was opened to fishing for a few months).  Here is the summary by the author, Dr. Robert Ahrens:

Results indicate that spillover and reopening effects around Johnston Atoll are strongly species-specific and sensitive to spatial scale, rather than uniformly positive across taxa. In the spillover analysis, interaction effects varied by both species and donut width, with some taxa showing positive near-boundary responses at selected widths, while others were neutral or negative.

This pattern is consistent with broader marine reserve evidence showing that, although protected areas often increase biomass and density within boundaries, fishery benefits outside boundaries depend on life-history traits, movement behavior, exploitation history, and reserve/boundary configuration (Halpern, 2003; Lester et al., 2009). It is also consistent with empirical studies demonstrating variable spillover among species and systems (Goñi et al., 2010; Lenihan et al., 2021; Russ et al., 2004).

Reopening effects in our analysis were similarly mixed: only a subset of species exhibited clear responses, whereas many taxa showed weak or non-significant changes, which is plausible given the short reopening window and limited inside-area sampling relative to the longer closure period. Taken together, these findings support a scale-aware, multi-species interpretation of reserve performance in which inference is based on effect sizes and uncertainty across distance definitions, rather than on an expectation of a single, uniform CPUE response to closure or reopening. (emphasis mine)

This is important data that can help us manage existing and designate new large protected areas around the world.  But the point we were trying to make in our Nature piece and that I'm hammering on again in this essay, is that we can't let fisheries science alone set the agenda for ocean policy.

Fisheries science institutions are oriented toward harvest and yield, and their tools—catch data, effort metrics—measure those outcomes . But they are poorly suited to capturing ecosystem health, biodiversity, or long-term recovery. As a result, what gets measured—and valued—is limited. Fisheries data may also reflect human behavior as much as ecological change. Shifts in technology, effort, and market conditions can influence catch rates in ways that obscure underlying ecological trends.  For example, it is astounding that NOAA has over 20 years of long line catch data -- but does that data capture changes in the human side of the fishery, or just the number of fish caught? 

The problem is not that fisheries scientists are involved—we want them involved and need their expertise—it is that they are often the only voices in decision-making contexts. This risks overlooking other forms of knowledge and evidence, including ecological monitoring, conservation science, and Indigenous perspectives.  I experienced this firsthand when I served on the NOAA Marine and Coastal Area-based Management Advisory Committee during the Biden years—which was disbanded as soon as Trump took office.

I encourage you to read the PIFSC analysis, but it is important to recognize its limits. It provides insight into fisheries responses, not a full assessment of ecological effectiveness. To truly evaluate MPAs, we need a broader, more inclusive scientific approach.  And so I repeat my plea for scientists, philanthropy, and NGOs to spend more time studying the protected areas in the US Pacific territories.