Shark Strongholds and Silent Coasts: A Comparative Analysis of Marine Reserve Efficacy in the Tropical Eastern and Central Pacific

Bryan White
Nov 28
20 min read

Abstract

The precipitous global decline of elasmobranch populations, driven largely by overexploitation and habitat degradation, has necessitated a critical re-evaluation of marine conservation strategies. While Marine Protected Areas (MPAs) are touted as the primary tool for biodiversity recovery, their effectiveness varies dramatically based on enforcement, location, and design. A landmark 2025 study led by the Charles Darwin Foundation and National Geographic Pristine Seas provides the most comprehensive assessment to date of shark and predatory fish assemblages across the Tropical Eastern Pacific (ETP). By utilizing stereo-Baited Remote Underwater Video systems (stereo-BRUVs) across seven MPAs, the research reveals a stark biogeographic and management dichotomy: remote oceanic islands—specifically the Galapagos, Malpelo, Clipperton, and Revillagigedo—function as the last global strongholds for high-density shark populations, while coastal MPAs, despite their protected status, exhibit signs of severe ecological depletion synonymous with "paper parks." This report synthesizes these findings with concurrent research from the Line Islands (Central Pacific) to deconstruct the mechanisms of resilience and collapse. It argues that geographical isolation, when coupled with strict no-take enforcement and specific habitat functions (such as nurseries), creates resilience. However, the study of Teraina Atoll demonstrates that remoteness alone is insufficient against the economic pull of global trade networks. The analysis highlights the critical role of "swimways" like the Eastern Tropical Pacific Marine Corridor (CMAR) and warns of emerging threats such as deep-sea mining in the Clarion-Clipperton Zone, concluding that the preservation of these apex predator reservoirs requires a paradigm shift from static boundary protection to dynamic, trans-national ecosystem management.

1. Introduction: The Apex of the Anthropocene Crisis

The world's oceans are currently undergoing a defaunation event of unprecedented speed and scale, with apex predators bearing the brunt of the impact. Sharks and rays, lineages that have survived five mass extinction events over 400 million years, now face a sixth, driven not by asteroids or volcanism, but by the industrial efficiency of human extraction. The removal of these architects of the marine environment is not merely a loss of charismatic megafauna; it represents the destabilization of the ocean's trophic structure, unraveling the complex web of interactions that maintain ecosystem health, carbon sequestration, and resilience against climate change.

In this context, the identification and protection of "shark strongholds"—areas where shark populations remain at or near historical baselines—has become a top priority for marine ecologists and conservationists. These areas serve as living laboratories, offering a glimpse into the "pristine" ocean of the past, and as genetic reservoirs that may one day fuel the recovery of depleted seas.

In late 2025, a pivotal study titled "Relative abundance and diversity of sharks and predatory fishes across Marine Protected Areas of the Tropical Eastern Pacific" was published in the journal PLOS ONE.¹ Led by Simon J. McKinley and Dr. Pelayo Salinas-de-León of the Charles Darwin Foundation, this research provided the first standardized, fishery-independent assessment of shark abundance across the vast Tropical Eastern Pacific (ETP) seascape.³ Spanning over 2 million square kilometers of ocean, the study compared the shark assemblages of remote oceanic islands against those of coastal Marine Protected Areas (MPAs) along the continental shelf of the Americas.

The findings were both exhilarating and alarming. They confirmed that the remote islands of the ETP—Galapagos (Ecuador), Malpelo (Colombia), Revillagigedo (Mexico), and Clipperton (France)—host some of the highest densities of sharks remaining on Earth.³ Yet, the study also revealed a "silence of the reefs" in the coastal MPAs. Despite being designated as protected areas, sites like Machalilla National Park in Ecuador and Caño Island in Costa Rica were found to be virtually devoid of the large predators that once patrolled them.⁴

This divergence forces a critical examination of the "MPA" label. Does protection work? Or is it merely a line on a map that creates the illusion of safety while extraction continues unabated? To answer this, we must look beyond the ETP. Concurrent research from the Central Pacific's Line Islands, specifically on Teraina Atoll, offers a chilling counterpoint. There, in one of the most remote places on the planet, a small-scale fishery drove a 75% decline in grey reef sharks in just 15 years.⁵

This report provides an exhaustive analysis of these interconnected narratives. It explores the oceanographic engines that power the ETP's oceanic oases, details the technological revolution of stereo-BRUVs that allowed for this census, and dissects the specific biological functions—such as the nursery role of Clipperton Atoll—that make these strongholds viable. Furthermore, it addresses the socio-economic failures driving the depletion of coastal reserves and outlines the urgent policy shifts required to prevent the silence of the remote islands from becoming the silence of the entire Pacific.

2. The Eastern Tropical Pacific Seascape: A Biogeographic Crucible

The Tropical Eastern Pacific (ETP) is a distinct marine biogeographic region, isolated from the Central Pacific by the "East Pacific Barrier"—a vast, deep expanse of open ocean that inhibits the migration of many shallow-water species. This isolation has fostered high levels of endemism and unique community assemblages. The region is governed by a complex interplay of currents, including the cool, nutrient-rich Humboldt Current flowing north from Antarctica, the warm Panama Current flowing south, and the subsurface Cromwell Current that upwells nutrient-laden waters when it collides with the region's massive underwater topography.⁶

2.1 The Oceanic Subprovince: Seamounts as Oases

The "oceanic subprovince" of the ETP comprises several archipelagos and isolated islands that sit atop the Cocos and Nazca tectonic plates. These islands are the peaks of underwater mountains, rising from depths of thousands of meters. They act as oases in the oligotrophic (nutrient-poor) open ocean, interrupting deep-water currents and generating local upwelling. This phenomenon, known as the "Island Mass Effect," fuels high primary productivity—blooms of phytoplankton that support zooplankton, baitfish, and ultimately, an inverted biomass pyramid where top predators dominate.

The key locations analyzed in the 2025 McKinley study represent the crown jewels of this province:

The Galapagos Archipelago (Ecuador): Situated at the confluence of the Humboldt, Panama, and Cromwell currents, the Galapagos is a UNESCO World Heritage site and a living laboratory of evolution. Its northern islands, Darwin and Wolf, are legendary for their biomass of Scalloped Hammerhead sharks (Sphyrna lewini). The archipelago's protection is robust, supported by satellite monitoring and a tourism economy that values a live shark at millions of dollars over its lifetime.³
Malpelo Island (Colombia): A stark, sheer-walled rock formation rising from the abyss, Malpelo is a fortress of biodiversity. It hosts some of the world's largest aggregations of Silky Sharks (Carcharhinus falciformis) and hammerheads. Designated as a Flora and Fauna Sanctuary, it is a strictly enforced no-take zone that has shown resilience even as surrounding waters are overfished.⁷
Revillagigedo Archipelago (Mexico): Often referred to as the "Galapagos of Mexico," this group of four volcanic islands (Socorro, Clarión, San Benedicto, Roca Partida) lies south of the Baja California peninsula. It is famous for its giant manta rays and distinct shark populations, particularly Silvertip Sharks (Carcharhinus albimarginatus) and Galapagos Sharks (Carcharhinus galapagensis). In 2017, it was designated as a massive marine reserve, banning all fishing in a 148,000 square kilometer area.⁹
Clipperton Atoll (France): The only true coral atoll in the ETP, Clipperton is a biogeographic anomaly. Located 1,000 km off the coast of Mexico, it is a "no man's land" of isolation. Its reefs are less developed than those of the Indo-Pacific but serve as a critical stepping stone for trans-Pacific migrants. Its isolation is its primary defense, though it also makes enforcement of French sovereignty difficult against illegal fishing fleets.¹⁰

2.2 The Coastal Subprovince: The Edge of Depletion

In contrast, the "coastal subprovince" includes the continental shelves of Central and South America. These waters are highly productive due to coastal upwelling but are also immediately adjacent to dense human populations, major industrial ports, and intensive fishing grounds. The interplay between MPAs and surrounding fisheries is intense here, with "edge effects" often penetrating deep into reserves.

The coastal sites surveyed in the McKinley study include:

Machalilla National Park (Ecuador): A park that includes significant marine zones but faces immense pressure from artisanal fleets and coastal development. While protected on paper, the enforcement of no-take regulations is often sporadic.⁶
Galera San Francisco Marine Reserve (Ecuador): Characterized by mangroves and rocky reefs, this reserve is ostensibly protected but allows for "mixed use," which often serves as a loophole for continued extraction.⁴
Caño Island Biological Reserve (Costa Rica): Located 15 km offshore, this reserve is a popular dive site. While it receives some protection due to tourism, it struggles with illegal incursions from the mainland and the impacts of agricultural runoff.⁶

2.3 Oceanographic Drivers of Abundance vs. Extraction

The persistence of shark populations in the oceanic islands is not solely a function of protection; it is also oceanographic. The Cromwell Current (Equatorial Undercurrent) hits the western flanks of the Galapagos and other seamounts, driving cold, nutrient-rich water to the surface. However, the McKinley study controls for this by comparing these islands to coastal zones that are also highly productive (e.g., upwelling zones off Ecuador). The stark difference in shark numbers—despite high primary productivity in both zones—points the finger squarely at anthropogenic extraction as the driver of decline in the coastal MPAs.

3. Methodology: The Stereo-BRUV Revolution

To accurately census apex predators, traditional methods like underwater visual census (UVC) by divers are often insufficient. Sharks are behaviorally complex; some species, like the Scalloped Hammerhead, can be shy and avoid divers (avoidance behavior), while others, like the Galapagos Shark, can be bold and attracted to divers (attraction bias), skewing counts. Furthermore, divers are limited by depth, time (bottom time), and the ability to survey deep or dangerous waters. To overcome these biases and generate a standardized dataset, the 2025 assessment employed stereo-Baited Remote Underwater Video systems (stereo-BRUVs).³

3.1 The Mechanics of BRUVs

A BRUV system consists of a rigid metal frame holding two high-definition video cameras mounted a fixed distance apart (typically 0.7 meters), converging on a bait canister suspended in the field of view. The canister is filled with a standardized bait—in this study, 1 kg of oily sardines—which creates an odor plume that travels downstream, attracting predators from a significantly wider area than visual survey methods alone.

Stereo-Calibration: The use of two cameras allows for photogrammetry. Specialized software (like EventMeasure) can triangulate points in the video to measure the length of the shark with high precision (root mean square error < 20 mm).⁶ This capability is revolutionary for conservation biology because it allows researchers to determine the age structure of the population. Knowing whether a reef is populated by sexually mature adults, sub-adults, or new recruits (juveniles) is critical for understanding the "source-sink" dynamics of the region.
MaxN Metric: To avoid the statistical sin of "double counting" (counting the same shark multiple times as it circles the bait), researchers use a metric called MaxN—the maximum number of individuals of a single species visible in a single frame of video at any one time.⁶ MaxN is a conservative measure of relative abundance. It inevitably underestimates the total number of sharks (since not all are in the frame at the exact same second) but provides a robust, repeatable index that is comparable across different sites and years.

3.2 Study Design and Scale

The McKinley et al. study represents a massive logistical undertaking. The team deployed 111 benthic BRUVs across the seven MPAs.⁶

Deployment Protocol: Each BRUV was left on the seafloor for at least 90 minutes. This duration is critical; studies have shown that it takes time for the scent plume to disperse and for cautious predators to approach the bait.¹²
Depth Standardization: The deployments were stratified by depth (typically 15–40 meters) to ensuring that comparisons between the reef habitats of the different islands were ecologically valid.
Data Volume: The videos recorded 18,771 individual fishes from 181 species and 52 families.⁶
Trophic Classification: Species were categorized into functional trophic groups to analyze the entire food web: Sharks, High-order Teleosts (e.g., groupers, snappers), Meso-predators, Planktivores, and Herbivores.⁶

3.3 Statistical Rigor

The study employed advanced multivariate statistics, specifically Permutational Multivariate Analysis of Variance (PERMANOVA), to test for differences in fish community structure. This allowed the researchers to say with statistical confidence that the differences observed between the oceanic and coastal assemblages were not due to random chance or local habitat variations, but were driven by the broad-scale factors of location (oceanic vs. coastal) and protection status.¹²

4. Results: The Oceanic Triumph

The data from the oceanic MPAs confirms their status as global anomalies. In an era where reef sharks are functionally extinct on 20% of the world's reefs (according to global surveys like Global FinPrint), the ETP oceanic islands host thriving, multi-species shark communities.³

4.1 Biomass Inversion and Apex Dominance

The BRUVs revealed that sharks were not just present in the oceanic MPAs; they were dominant. The relative abundance (MaxN per hour) of sharks in these locations was among the highest recorded anywhere on Earth.¹⁴ In many deployments, the "MaxN" was limited only by the field of view of the camera—sharks were crowding the frame.

Species Richness: The oceanic islands supported a diverse guild of predators, including Scalloped Hammerheads (Sphyrna lewini), Galapagos Sharks (Carcharhinus galapagensis), Silvertip Sharks (Carcharhinus albimarginatus), Tiger Sharks (Galeocerdo cuvier), and Whitetip Reef Sharks (Triaenodon obesus).
Biogeographic Latitudinal Gradient: The study found a distinct latitudinal split in species dominance:
Southern MPAs (Galapagos, Malpelo): These equatorial sites were dominated by Scalloped Hammerheads. These islands serve as critical aggregation sites for schooling hammerheads. The reasons for this schooling behavior are complex, likely involving magnetoreception (navigating by the magnetic signatures of the volcanic seamounts) and social functions (mating selection).³
Northern MPAs (Revillagigedo, Clipperton): These sites were dominated by Silvertip Sharks. This species, a powerful reef predator, prefers the slightly different oceanographic conditions of the northern ETP. This differentiation highlights the importance of protecting multiple strongholds; saving Galapagos alone would not protect the unique Silvertip-dominated systems of the north.³

4.2 Clipperton Atoll: The Pacific Nursery

One of the most profound and novel insights from the study concerns Clipperton Atoll. While Galapagos and Malpelo are famous for their schools of massive adult sharks, Clipperton told a different demographic story.

The Juvenile Signal: The stereo-video measurements revealed that the vast majority of Carcharhinus galapagensis (Galapagos sharks) at Clipperton were of juvenile sizes.³
Ecological Function: This strongly suggests that Clipperton functions as a crucial nursery ground. Juvenile sharks are highly vulnerable to predation, including cannibalism by larger adults of their own species. They require sheltered areas with abundant food and fewer large predators. The lagoon and shallow reef terraces of Clipperton appear to provide this sanctuary.
Regional Connectivity: The presence of a nursery at Clipperton implies connectivity. Sharks born here likely migrate to other areas (like Revillagigedo or even further afield) as they mature. If Clipperton were compromised by fishing or deep-sea mining, the recruitment of adults to other parts of the ETP could fail. This highlights the "source-sink" dynamics of the region—Clipperton is a vital source. Historical accounts from the 1960s (Limbaugh) described juvenile Galapagos sharks at Clipperton as so abundant and aggressive they would bite at oars; the 2025 data confirms this high density of young sharks persists, provided the atoll remains isolated.¹⁶

4.3 Malpelo and Revillagigedo: The Adult Fortresses

In contrast to the nursery signal at Clipperton, the shark populations at Malpelo and Revillagigedo were skewed towards large, sexually mature adults.³

Foraging and Mating: These sites serve as aggregation points for mating and foraging. The vertical walls of Malpelo, plunging into the abyss, allow pelagic sharks to access deep scattering layers of squid and fish at night while schooling for social reasons during the day.
Resilience: The high biomass of large adults indicates a population that has survived the perilous juvenile years. However, these aggregations are also massive targets. A single illegal longline set through a hammerhead school at Malpelo can remove reproductive stock that took decades to build. The study confirms that strict enforcement at these sites has successfully maintained these "breeding banks."

4.4 The "Pristine" Baseline

The abundance of high-order teleosts (groupers like the Leatherbass, Dermatolepis dermatolepis, and Bluefin Trevally) mirrored the shark data. These islands represent a "baseline" of what the Pacific looked like before industrial fishing. In these systems, top-down control is the norm. The predators regulate the meso-predators, maintaining biodiversity. The study notes that in these oceanic MPAs, fish communities were abundant and diverse across all trophic levels, debunking the idea that high predator numbers suppress overall biodiversity; rather, they structure it, preventing any single species from monopolizing resources.³

5. Results: The Coastal Collapse

If the oceanic islands are a window into the past, the coastal MPAs are a mirror of the present crisis. The findings from Machalilla, Galera San Francisco, and Caño Island were sobering and serve as a warning for marine management globally.

5.1 The Absence of the Apex

In stark contrast to the offshore islands, the coastal MPAs revealed few to no large predators.³

Data Void: Despite high deployment effort (over 30 BRUV drops in coastal zones), large sharks were virtually absent from the coastal data sets.
Low Abundance: Not only were sharks missing, but the overall abundance of fish was significantly lower. The "High-order Teleost" category (large snappers and groupers) was also depleted.

5.2 Fishing Down the Food Web

The community structure in the coastal MPAs exhibited the classic signs of "fishing down the food web," a concept introduced by fisheries scientist Daniel Pauly.

Mechanism: Fisheries typically target the largest, most valuable species first (sharks, giant groupers). Once these are depleted, they move to the next trophic level (snappers, jacks), and eventually to herbivores and planktivores.
Evidence: The coastal MPAs were dominated by smaller, lower-trophic level fish. The absence of top predators normally releases meso-predators (smaller groupers, wrasses) from predation pressure, initially causing their numbers to spike. However, in the ETP coastal sites, even these meso-predators appeared suppressed, suggesting that fishing pressure is so intense it is stripping the reef from the top down and the bottom up simultaneously.¹²

5.3 The Failure of "Paper Parks"

The study authors explicitly link these findings to management failures. While these areas are designated as MPAs, they often lack the "No-Take" status or the enforcement capacity of their oceanic counterparts.

Mixed-Use Zones: Places like Galera San Francisco allow for certain types of "artisanal" fishing. The data suggests that even "sustainable" artisanal fishing, when aggregated across hundreds of vessels, is incompatible with the maintenance of apex predator populations.⁴
Enforcement Gaps: Coastal MPAs are accessible. A fisherman in a small panga can enter, set a gillnet, and leave within hours. In contrast, reaching Malpelo or Clipperton requires an ocean-going vessel and significant fuel, creating a natural barrier to entry for the smallest (and most numerous) illegal operators.
Pollution and Habitat Loss: Coastal zones also suffer from sedimentation, agricultural runoff, and coastal development, stressors that are largely absent in the oceanic islands.

6. The Line Islands Counterpoint: When Remote Isn't Enough

While the McKinley study suggests that remoteness aids conservation, it is not a panacea. A concurrent study by Maurice Goodman et al. (2025) serves as a critical control case, demonstrating that isolation without strict protection is fragile. This study focuses on the Northern Line Islands, specifically Teraina (Washington Island) in the Central Pacific, part of the nation of Kiribati.⁵

6.1 The Teraina Anomaly

Teraina is as remote as it gets—thousands of kilometers from major continents. Yet, the Goodman study found a 75% decline in grey reef sharks (Carcharhinus amblyrhynchos) over just 15 years.⁵

The Cause: Unlike the strictly protected and largely uninhabited Galapagos reserves, Teraina supports a small community of inhabitants. The study traces the decline to a specific economic shift: the transition from subsistence fishing to commercial exploitation.
The Shark Fin Trade: Around the year 2000, local fishers began targeting sharks not just for meat (a low-value subsistence food), but for fins to sell to visiting foreign collecting vessels. This connection to the global market (trans-national trade) incentivized the rapid depletion of the local shark stock.⁵

6.2 The Fragility of "Safe" Places

The Line Islands study shatters the illusion that distance equals safety.

Small Effort, Massive Impact: The collapse on Teraina was driven by a very small number of fishers (approximately 17 fishers using canoes and small boats with outboard motors).¹⁷ This demonstrates the extreme vulnerability of reef sharks. Because sharks are slow-growing, late-maturing (K-selected species), and have high site fidelity, even a modest extraction rate can drastically outpace their reproductive capacity.
Implications for ETP: This reinforces the findings of the McKinley study regarding the coastal MPAs. If a handful of canoe fishers can wipe out sharks on remote Teraina, the intense pressure from artisanal fleets along the densely populated coasts of Ecuador and Costa Rica makes the depletion of coastal MPAs almost inevitable without draconian enforcement and no-take designations. It proves that "artisanal" does not mean "benign."

7. Biological Profiles of the Key Architects

To understand the stakes of these findings, we must understand the animals involved. The strongholds are protecting specific lineages, each with unique life histories and vulnerabilities.

**7.1 Scalloped Hammerhead (*Sphyrna lewini***)

Status: Critically Endangered (IUCN).
Role: Large coastal/semi-oceanic predator.
Behavior in ETP: They are famous for forming massive schools around seamounts like Darwin Island in Galapagos and Malpelo. These schools are predominantly female.
Vulnerability: They are obligate ram ventilators (they must keep swimming to breathe) and are extremely susceptible to capture stress. Unlike some sharks that can survive catch-and-release, hammerheads often die from the metabolic exhaustion of fighting a line. They also have a complex life cycle involving coastal nurseries (often in mangroves) and oceanic adult habitats. The coastal depletion found by McKinley is terrifying for this species—it implies their nurseries are being emptied, cutting off the supply of new recruits to the oceanic schools.

**7.2 Galapagos Shark (*Carcharhinus galapagensis***)

Status: Least Concern globally, but locally vulnerable.
Role: The quintessential island shark. They are large, aggressive requiem sharks that dominate the reef ecosystem in the ETP.
Behavior: They are known for cannibalism, which may drive the spatial segregation of juveniles (at Clipperton) from adults (at Malpelo/Galapagos). They are curious and bold, making them easy targets for fishers.
Historical Note: At Clipperton, their historic aggression towards boats (Limbaugh, 1963) is a testament to the density they can achieve in the absence of humans.¹⁶

**7.3 Silvertip Shark (*Carcharhinus albimarginatus***)

Status: Vulnerable.
Role: A powerful reef predator, often found deeper than the Galapagos shark.
Stronghold: The Revillagigedo Archipelago and Clipperton. Their dominance in the northern ETP highlights the need for a network of MPAs that covers different latitudes to protect the full diversity of shark species in the region.

8. Ecological Implications: The Cost of Silence

The loss of sharks in the coastal ETP and the Line Islands is not just a loss of charismatic megafauna; it is a functional degradation of the ecosystem.

8.1 Trophic Cascades

The removal of apex predators triggers trophic cascades.

Mesopredator Release: Without sharks, populations of mid-sized predators (like groupers or rays) may expand. These mesopredators then overconsume herbivores (parrotfish).
Algal Phase Shifts: With fewer herbivores, algae can overgrow coral reefs, preventing coral settlement. This reduces the reef's resilience to thermal stress (bleaching). In the ETP, where El Niño events already cause massive coral mortality, the lack of sharks reduces the reef's ability to bounce back.

8.2 Blue Carbon and Climate Resilience

Sharks are increasingly recognized as "Climate Heroes".¹⁹

Carbon Sequestration: By controlling grazers (like turtles on seagrass or fish on reefs), sharks maintain the structural complexity of habitats that sequester carbon.
Nutrient Cycling: Pelagic sharks (like Hammerheads) feed in the open ocean and defecate on the reef, transferring distinct nitrogen and phosphorus isotopes from the deep sea to the shallow coral ecosystem. This "biological pump" fertilizes the reef. The depletion of these vectors breaks a critical nutrient loop that sustains reef productivity.

9. Emerging Threats: The Deep Sea Mining Horizon

While overfishing is the current crisis, the report highlights a future threat: Deep-Sea Mining (DSM).²⁰

The Overlap: The Clarion-Clipperton Zone (CCZ), a vast area of the Pacific seabed targeted for polymetallic nodule mining, sits directly adjacent to the Clipperton and Revillagigedo strongholds.
Sediment Plumes: Mining would generate plumes of sediment that could drift onto these isolated reefs, smothering corals and disrupting the visual hunting of sharks.
Noise Pollution: The noise from mining operations could interfere with the sensory biology of sharks, driving them away from these critical seamounts.
Vulnerability: A 2025 study led by Aaron Judah found that deep-sea mining could threaten at least 30 species of sharks and rays, many of which overlap with the mining leases in the Pacific. The connectivity shown between Clipperton (a nursery) and the wider ETP means that mining impacts at Clipperton could have cascading effects on shark populations thousands of kilometers away in the Galapagos.²⁰

10. Socio-Economic Dimensions and Management

The dichotomy between the thriving oceanic MPAs and the failing coastal ones is ultimately a socio-economic story.

10.1 The "High Cost" of Success

The success of the Galapagos and Malpelo is expensive.

Technology: These parks utilize satellite monitoring (AIS/VMS), radar, and regular naval patrols to intercept illegal vessels.
Tourism Revenue: The "shark diving" industry provides the economic engine. A live shark in the Galapagos is estimated to be worth millions of dollars over its lifetime in tourism revenue, compared to a few hundred dollars for its fins. This economic valuation creates political will for protection.

10.2 The Coastal Dilemma

Coastal MPAs lack this revenue stream. They are often embedded in communities with high poverty rates where fishing is a survival strategy.

Conflict: Restricting fishing in Machalilla creates direct conflict with local voters. Without alternative livelihoods (like ecotourism), enforcement becomes politically toxic and practically difficult.
Trust: Managers often sell MPAs to fishers with the promise of "spillover"—that the reserve will replenish adjacent fishing grounds. However, if the reserve is too small or poached too heavily (as the data suggests), the recovery never happens, and trust erodes.

10.3 The Global Trade Nexus

The Teraina study proves that local management is helpless against global demand.⁵

Supply Chains: As long as shark fin commands a high price in Asian markets, the economic gravitational pull will reach even the most remote atolls.
Solution: The report argues that management must be trans-national. Bans on the trade of fins are more effective than bans on fishing in remote areas where no one is watching.

11. Future Directions and Policy Recommendations

The 2025 findings necessitate a paradigm shift in marine conservation.

11.1 From Islands to Corridors

Protecting the islands is not enough. Sharks migrate. The Scalloped Hammerheads of Galapagos migrate to Cocos Island (Costa Rica) and Malpelo.

Swimways: The creation of the Eastern Tropical Pacific Marine Corridor (CMAR) is a vital step. This initiative aims to protect the "swimways" between these MPAs. The data supports this: since adults are in one place (oceanic) and nurseries in another (coastal), the corridors connecting them must be protected from industrial longliners.

11.2 Upgrading Coastal MPAs

The coastal MPAs need a "re-boot."

No-Take Zones: Mixed-use is failing. Coastal MPAs need core, strictly enforced no-take zones to allow biomass to recover.
Enforcement Technology: The cost of surveillance technology (drones, shore-based radar) is dropping. This must be deployed in coastal reserves to detect illegal incursions.

11.3 Citizen Science

The use of citizen science, as seen in the "Sharklogger" network (though primarily in the Caribbean), offers a model for the ETP. Engaging divers to record shark sightings can provide cost-effective, long-term data to supplement BRUV surveys and foster local stewardship.²²

11.4 The 30x30 Goal

The global goal to protect 30% of the ocean by 2030 (30x30) risks creating more "paper parks."

Quality over Quantity: The McKinley study shows that status is irrelevant without enforcement. Counting a depleted coastal reserve towards the 30% target is a statistical lie. The focus must shift to "High-Quality MPAs" that demonstrate biological recovery.

12. Conclusion

The 2025 assessment of the Tropical Eastern Pacific serves as both a eulogy and a blueprint. The eulogy is for the coastal ecosystems of the Americas, where the functional role of the shark has been extinguished by the relentless pressure of "fishing down the food web." The silence of the stereo-BRUVs in Machalilla and Galera San Francisco is a deafening indictment of current management practices.

However, the blueprint lies in the oceanic islands. The Galapagos, Malpelo, Revillagigedo, and Clipperton stand as testaments to the resilience of nature. They prove that when the pressure is removed—whether by the tyranny of distance or the vigilance of enforcement—the ocean remembers how to thrive. These shark strongholds are not just biological oddities; they are time capsules, preserving the genetic and ecological blueprints necessary to rebuild the ocean.

The challenge now is two-fold: to defend these remaining fortresses against the encroaching threats of illegal fleets and deep-sea mining, and to export their model of strict protection back to the coastlines where it is needed most. As Dr. Salinas-de-León noted, these islands provide a glimpse of what a healthy ocean looks like.³ The question remains whether humanity has the political will to turn that glimpse into a global vision.

Table 1: Comparative Shark Abundance and Diversity in Selected ETP MPAs (2025)

MPA	Subprovince	Dominant Species	Primary Ecological Function	Protection Status	Relative Abundance (MaxN)
Galapagos	Oceanic	Scalloped Hammerhead (S. lewini)	Adult Aggregation / Foraging	Mixed (High Enforcement)	Very High
Malpelo	Oceanic	Scalloped Hammerhead (S. lewini)	Adult Aggregation / Mating	Strict No-Take	Very High
Clipperton	Oceanic	Galapagos Shark (C. galapagensis)	Nursery (Juvenile dominant)	Remote / Isolated	High
Revillagigedo	Oceanic	Silvertip Shark (C. albimarginatus)	Adult Aggregation	Strict No-Take	High
Machalilla	Coastal	N/A (Rare sightings)	Depleted Ecosystem	Mixed (Low Enforcement)	Negligible
Galera San Francisco	Coastal	N/A (Rare sightings)	Depleted Ecosystem	Mixed (Low Enforcement)	Negligible
Caño Island	Coastal	Whitetip Reef Shark (T. obesus)	Recovering / Transitory	Biological Reserve	Low/Moderate

Data synthesized from McKinley et al. (2025) ¹ and Darwin Foundation Reports.³

Table 2: The Line Islands Anomaly (Teraina Atoll)

Parameter	2013 Status	2025 Status (Post-Study)	Change Factor
Grey Reef Shark Population	Baseline (Estimated)	-75% Decline	Commercial Finning
Primary Fishing Driver	Subsistence / Cultural	Export (Shark Fin Trade)	Global Market Access
Fishery Scale	Canoe / Small Boat	Motorized Skiffs	Technological Creep
Conclusion	Remote = Safe	Remote = Vulnerable	Failure of Isolation

Data derived from Goodman et al. (2025).⁵

Works cited

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