MARINE PROTECTED AREAS CAN BENEFIT TUNA, BUT...

 

Anyone who has followed this blog for a while probably knows that I’m a skeptic when it comes to the worth of no-take marine protected areas. 

While I believe that time and area closures, gear restrictions, and similar measures can be effective fishery management tools, I also believe that management measures should be crafted to address specific and clearly defined problems.  Prohibiting all bottom fishing over a particular set of banks, ledges, or reefs, in order to protect spawning aggregations of grouper, for example, could be an entirely reasonable management measure.  Shutting down all fishing in such a place, including trolling for billfish, dolphin, and tuna 300 feet above such protected bottom, in the surface layers where grouper never go, is unacceptable management overreach.

I’m particularly critical of such indiscriminate closures when they prohibit angling for highly migratory species in a small geographic area that such fish might transit in the course of a day, if not a few hours; such ephemeral protections provide no real protection to pelagic fish, but could work real hardship on anglers if they shut down readily accessible fishing grounds, and make it a practical impossibility for fishermen to target their chosen species without embarking on long trips or shifting their boats to ports farther from home.

Even a week ago, I would have said that no-take marine protected areas have no place at all in highly migratory species management, but a recently released scientific study shows that is not true—although the area studied differs substantially from the typical MPA.

It’s nice to know that my skepticism was shared by many in the scientific community; the paper that describes the study, “Spillover benefits from the world’s largest fully protected MPA,” which appeared in the journal Science on October 20, admits in its abstract that

“Previous work had cast doubt on the potential for marine protected areas (MPAs) to provide refuge and fishery spillover benefits for migratory species as most MPAs are small relative to the geographic range of such species.”

But it turns out that if the MPA is large enough, such benefits can occur.  Dr. Sarah Medoff of the University of Hawaii, an author of the paper, expressed surprise at her study’s findings, saying,

“I think the common perception of no-fishing zones is that they really are only going to benefit less mobile species, like corals or lobsters…And so when we found that there was this positive benefit for bigeye and yellowfin, that was completely shocking to us.”

The study focused on yellowfin and bigeye tuna, and the protections and benefits provided by the Papahanaumokuakea (formerly, the Northwest Hawaiian Islands) Marine National Monument, which is located, as its name suggests, northwest of the eight larger islands that most people probably think of when they hear the name “Hawaii.”  The national monument encompasses 583,000 square miles, an area nearly four times the size of the State of California, and is the world’s largest no-take marine protected area.

The marine national monument was only about one-quarter of its current size when President George W. Bush created it in 2006; it was expanded to its current boundaries in 2016 by President Barak Obama.  That expansion turned out to be the key to the recently-released study.

The researchers conducted the study by examining records maintained by the National Marine Fisheries Service, which recorded the catch of tuna longliners that fished within 600 nautical miles of the marine monument during the years 2010 through 2019.  It turned out that after the monument was expanded in 2016, catch rates increased substantially.

The catch rate of yellowfin tuna by vessels fishing outside the Papahanaumokuakea monument increased by 54% between 2016 and 2019, with the greatest increases seen by boats setting their lines between 100 and 200 nautical miles from its borders.  The catch rate of bigeye tuna increased by a much smaller but still significant 12%.  A similar increase was not observed in the catch rates of vessels fishing outside the original borders of the marine monument during the years 2010 through 2016, suggesting that the improved catch rates were a direct result of the monument’s expansion.

An interesting sidenote to the findings was that the monument wasn’t created to benefit the yellowfin or bigeye tuna stocks.  As researcher Dr. John Lynham of the University of Hawaii noted,

“It’s important to point out that this protected area was not created with the intent of protecting tuna…This fish benefit was a happy accident of the initial intent, which was to protect biodiversity and culturally important areas.””

As to why the tuna benefitted from the marine monument, another of the paper’s authors, Dr. Jennifer Raynor of the University of Wisconsin, suggested a pair of possible explanations:

“The protected area could be doing one of two things.  The first is that these iconic fish populations are increasing because the areas provide nurseries for baby fish, and some of them are spilling over into nearby areas.  A second reason may be that fish are just finding a safe place to aggregate, near the protected area, where they can’t be caught.”

Luck may also have played a role, something Dr. Raynor admits.  While the marine monument wasn’t intended to benefit tuna, it just so happened that its shape conforms to the east-west pattern of tuna movements.  Yet, accident or not, the Papahanaumokuakea monument has proven to be a boon to both the tuna and Hawaii’s tuna longline fleet.  There is now little question that a no-take marine protected area can, if large enough and properly oriented, benefit tuna populations.

Having said that, there is still the need to keep the study’s conclusions in context.

The Pacific Ocean is a huge expanse of water, and the scene of much recent volcanic activity; much of it is dotted with volcanic islands that rise from the deep ocean floor, with banks and seamounts that mark the location of ancient islands that have since been eroded away by the sea, and with atolls where the remains of ancient volcanoes have not yet completely surrendered to the waves.  It is a place where a national monument 1,350 nautical miles long can comfortably fit amid the islands and the emptiness, and leave more than enough room for fishermen to ply their trade.

The Atlantic Ocean is a narrower sea, and one far less amenable to such large-scale closures.  The distance between the northernmost point on the Maine coast and the southernmost tip of mainland Florida is less than 1,600 miles; a no-take MPA the size of Papahanaumokuakea would, in a north/south orientation, run almost the entire length of the U.S. East Coast.  Yet there is no evidence to suggest that anything significantly smaller would provide meaningful benefits, either to highly migratory tuna stocks or to the fishermen who pursue them.

Despite that, there are reasons to worry that various marine conservation groups still seek to create much smaller, ineffective no-take MPAs along the Atlantic coast.

The concerns arose with the 30x30 movement, an international effort to protect 30% of the Earth’s lands and waters by the year 2030.  On its face, the movement is innocuous and, in all honesty, probably a good idea.  In the United States, the concept was embodied in an executive order issued by President Joseph Biden on January 27, 2021, and later in a multi-agency report titled “Conserving and Restoring America the Beautiful,” which was a balanced and well-reasoned document, but also contained the observation that

“Ocean stakeholders also noted that many of the nation’s marine protected areas are located in the Western Pacific.”

The implication of such comment is clear; some “ocean stakeholders” are eager to see marine protected areas created in other regions, as well.  That intention was confirmed in a letter dated October 7, 2021, which was signed by 44 marine scientists and addressed to the Secretary of Commerce, the Secretary of the Interior, and other leading environmental officials.  Such letter broadly supported 30x30 and, in that context, the creation of additional no-take MPAs, saying

“We must take bold steps to halt and reverse the trajectory of the threats to our ocean and communities—now.  Marine protected areas (MPAs) represent a powerful tool to do so.  Below, we offer recommendations to leverage marine protected areas to achieve the bold, inclusive vision laid out in America the Beautiful for oceans and coasts….

“…MPAs are ocean areas set aside primarily for the long-term conservation of nature, and provide associated benefits to people such as enhanced fish stocks and cultural ecosystem services like mental and physical health, sense of place, and identity formation.  They remove direct human pressures, protecting undisturbed areas and allowing disturbed areas to recover.  Importantly, research has shown that fully-protected MPAs (where all abatable destructive or extractive activities are removed) and highly protected MPAs (where only light destructive or extractive activities with low impact are allowed) are more effective than lightly or minimally protected areas at restoring and preserving biodiversity and enhancing ecosystem resilience in the face of climate change…

“…MPAs currently cover 26% of U.S. federal and state waters, including inland bays and estuaries.  However, 99% of these protections are in the remote Pacific, leaving most of the coastal communities of the continental US and US Caribbean without access to MPAs and leaving those ecosystems and habitats vulnerable to overexploitation, degradation and destruction..

“Because highly to fully protected areas are the most effective type of MPA for delivering the goals of America the Beautiful, we recommend the Administration work to establish more of these effective conservation measures in U.S. waters…”

Thus, with respect to tuna, it seems that we have almost come full circle.  In the past, the prevailing belief was that marine protected areas were of little benefit to such highly migratory species, but recent research indicates that, if an MPA is large enough, and properly sited, it can benefit both tuna stocks and tuna fishermen.  However, as the Papahanaumokuakea-related longline data collected prior to 2016 shows, such benefits are not provided by smaller MPAs.

Yet MPAs advocates still call for the creation of fully-protected MPAs, in which fishing for all species, including tunas, would be prohibited, in areas such as the US Caribbean and the Gulf and Atlantic coasts, even though such waters lack the vast expanses that would permit the creation of MPAs large enough to benefit highly migratory species while still offering adequate fishing opportunities in unprotected waters.

Such arbitrary closures make no sense.

If very large and well-sited MPAs can provide real benefits to the tuna and tuna fishermen of the Pacific Ocean, then such existing MPAs should be maintained, and the creation of new protected areas considered.  But, where the creation of such vast closed areas is not a practical option, the notion of fully-protected ocean areas should be abandoned in favor of more directed restrictions that address the problems at hand.