The Gulf That Keeps Getting Saved

Golfo Dulce is one of a handful of tropical fjords on the planet. A shallow sill, an underwater ridge, almost closes the gulf's mouth. Behind it the deep inner basin sits still, its deepest 100 meters starved of oxygen, a quiet pocket of warm water on the south Pacific coast of Costa Rica. About 1,028 marine species have been recorded in the gulf, roughly a fifth of everything known from the country's Pacific, and for groups like the molluscs and the marine worms, it holds more than twice as many species per square kilometer as the Golfo de Nicoya to the north. It is the only place on Earth where humpback whales from both the northern and southern hemispheres come to give birth. In its mangrove shallows, scalloped hammerheads are born by the thousands.

A place this singular has been protected on paper again and again. On land first, then for its fish, then for one shark, and soon for its corals.

When the road came

For most of its history the forest down the spine of the Osa Peninsula survived because the land was steep, wet, and hard to reach. It was not empty. Pre-Columbian people worked the peninsula's gold-bearing rivers, and the Ngäbe hold an indigenous territory inside the forest today. But the terrain that made the interior hard to reach also made it useless for the plantations that cleared the flats. When the United Fruit Company built its banana enclave on the gulf from 1936, it laid out a port at Golfito and planted the level river deltas, leaving the ridges alone. The steep ground was no use for bananas, so the clearing that took the lowlands never climbed the peninsula.

What eventually opened the forest was access. Gold strikes and land-hungry settlers pressed in through the mid-20th century, and the Interamerican Highway reached the region in 1960. A US timber company, Osa Productos Forestales, bought some 47,000 hectares of the peninsula from former United Fruit holdings, then left most of it idle, which drew squatters onto the land. The standoff turned violent in the early 1970s, and the State expropriated the company, carving Corcovado National Park out of its ground in 1975.

In 1978 the government created the Reserva Forestal Golfo Dulce by decree. The reserve runs down the forested spine of the Osa Peninsula, wrapping Corcovado and reaching up around the head of the gulf. The decree placed those hills under the forest regime, which bars clearing them without state permission, and declared the public land inside the reserve inalienable. The trigger, named in the decree itself, was a new road. A track had just been cut linking the Interamericana at Piedras Blancas to Rincón and Puerto Jiménez, and it "ended the isolation that previously gave these lands natural protection." The reserve was meant to protect the forest as the new road opened the way in.

The protection unraveled slowly, from within the State itself. The Instituto de Desarrollo Agrario, the government's own settlement agency, ran a colonization estate that overlapped the reserve, and it kept handing out parcels of land the 1978 decree had frozen as inalienable public forest, land no agency could lawfully title to a private owner. When occupants later went to court for those titles, the Procuraduría found that many of the claims did not hold up: transfers dated to after the reserve was created, survey plans missing or drawn up too late, even two settlers claiming the same parcel. One case shows how far the paperwork drifted. The agency's resolution granted a settler 12 hectares, while the deed it issued recorded 126. The gap was so large the agency referred the matter for criminal prosecution, and the Procuraduría flagged it.

Cancelling a title ran on a clock; recovering the land did not. Annulling any one of the State's own past adjudications meant suing within a fixed deadline, and those deadlines kept lapsing. As early as 2002 the Procuraduría was warning, on one parcel, that the clock was running out; in 2019 a court found one such failure to act in time unlawful. But the deeds were void from the start. Public forest inside the reserve cannot be privately owned at all, so the titles never actually made the land private, and letting the deadline to strike them from the register lapse did not make them valid. The State can lose the narrow fight to cancel a particular deed and still keep its claim to the ground itself, because that claim, over inalienable public land, never expires.

The fight moved to the legislature. When a bill surfaced to legalize the occupations, the Procuraduría opposed it hard, noting that some occupants carried forest-crime records and that some parcels overlapped the public maritime strip or indigenous land, and warning against a law that would reward "usurpadores de dominio público" (usurpers of public land). Decades on, who holds the titled ground inside the reserve is still unsettled.

Closing the gulf to the fleets

Everything protected so far had been land. The 1978 reserve was joined by a wildlife refuge over Golfito's forested watershed in 1985, by Piedras Blancas National Park in 1991, part of it bought back for the state by a campaign of Austrian donors, and by the Osa Conservation Area that tied the peninsula's reserves together the same year. The open water of the gulf had no protection at all.

INCOPESCA drew the first marine line in 2010, declaring Golfo Dulce an Área Marina de Pesca Responsable, presented at the time as the largest managed-fishing area in Central America. The area was not imposed over the fishers' heads. Their artisanal associations had pushed for it, and some license holders gave up gear to get it; nine Golfito permit-holders surrendered their gillnet and shrimp-trawl rights the year before the area was declared. The plan split the gulf into three zones and worked from a positive list. Only named artisanal and sport gear was allowed: hand lines, small hooks. Everything left off the list, the industrial fleets, the longliners, the trawl nets, was shut out. Shrimp fishing, which depends on dragging or netting, was closed. Most of that gear was still legal elsewhere on the coast. The 2010 declaration set up a standing Monitoring Commission to watch the water, and a 2014 reform held the sport catch to 5 fish a day per boat, however many anglers were aboard.

It was a managed-use area rather than a no-take reserve, and existing licenses for other gear were grandfathered until they expired. Its scientific footing was thin enough that, years later, the agency admitted in court that no technical study justified the gear ban, which rested instead on the participatory process that created the area.

The ban left the gulf's artisanal shrimpers with no legal way to work. Trawling was already gone from the gulf, and in 2013 the Sala Constitucional, the constitutional court, struck down shrimp trawling across the whole country, barring any new, renewed or reactivated trawl license and letting existing ones run only until they expired. The fishers proposed a different net, the suripera, and asked INCOPESCA to approve it; the agency classified it as barred trawl gear and refused, and the courts upheld that refusal on every challenge.

Inside the gulf, the trawl ban holds. Nationally its future is unsettled: a bill to reactivate trawling cleared constitutional review in 2020, a 2022 amendment reopened a path through a research exemption, and a challenge to that amendment was dismissed in November 2025.

The bans did not always stop the boats. In 2013 four vessels, La Zorra, Navegante del Sur, El Tracher and El Veloz, were still dragging for shrimp around the gulf. The trawlers had gone to court to overturn the responsible-fishing area, and when their permits expired mid-case an appeals tribunal ordered INCOPESCA to keep them valid until the suit was resolved. An advocate for the artisanal fishers asked the constitutional court to annul that extension as a breach of the 2013 trawl ban. The court rejected the case outright: an amparo, the fast-track constitutional complaint, cannot overturn another court's ruling, so the fight had to go back to that tribunal.

Whatever the rules say, on the water they are broken in the open. A separate INCOPESCA rule bars longlines baited with live fish within 30 nautical miles of shore, because live bait is what draws in the sharks and sea turtles the rule exists to spare. The sportfishing foundation FECOP has counted 10 to 15 longliners at a time still working inside the gulf's closed zone, their lines running up to 20 kilometers. FECOP is an advocacy group, and the government keeps no count of its own to weigh against it.

In 2025 the conservation group Earthrace ran patrols along the Pacific coast as far south as Golfo Dulce. Every longline unit its crew boarded was breaking some rule, three-quarters of the hooks baited with live fish, the banned bait that takes sharks and turtles. One boat, the Maricruz II, carried live bait on half its hooks 22 miles out, well inside the 30-nautical-mile line. Its founder, Pete Bethune, called what the survey found "un patrón claro de incumplimiento" (a clear pattern of non-compliance). Earthrace is a private group too. What the State does not publish is its own record: how many boats the Coast Guard and INCOPESCA have stopped, cited or sanctioned in these waters. What patrolling there is depends on a converted Second World War vessel Earthrace runs, working alongside the park rangers who hold the legal power to act.

Baby sharks

The scalloped hammerhead is listed critically endangered worldwide, and the gulf's mangrove shallows are one of the nurseries it depends on. The pups spend their first months in the sheltered bays before moving out to sea; tracking has followed them from the gulf to Isla del Coco, the shark-massed island more than 500 kilometers out in the Pacific.

Two marine biologists made the case for protecting the nursery. For years Ilena Zanella and Andrés López of Misión Tiburón worked the shallows from a small boat, documenting the nursery year after year. The fishers moved before the government did: in March 2018 the local Fishing Commission closed bottom longlines from May to October on its own initiative. Two months later the State turned the science into law, declaring the Santuario del Tiburón Martillo Golfo Dulce, the country's first shark sanctuary, with a ban on catching, moving or selling hammerheads inside it. Misión Tiburón won a Whitley Award in 2019, the conservation prize known as a Green Oscar, and Mission Blue named the gulf a Hope Spot the same year.

The sanctuary is a shallow band hugging the gulf's shore, out to the rear edge of the seagrass and coral or to six meters' depth. It follows that shore from Punta Banco, on the eastern side of the mouth, around the head to Cabo Matapalo on the west, a fringe of inshore water rather than the whole gulf. The 2018 decree drew that line but then stated an area, 4,210 hectares, that did not match it. A 2022 decree fixed the figure at 15,430.9 hectares, added thousand-meter buffers at the mouths of the Rincón, Agujas, Tigre and Platanares rivers, and took in the marine strip of Piedras Blancas National Park, whose waters reach the gulf's northern shore. The 2022 decree also upgraded the shark's status in its own text, from endangered to critically endangered. The next year the protection went national: in 2023, a total ban on capturing, landing or trading hammerheads in any Costa Rican water, grounded in CITES, the global treaty that lists the species.

Where the mothers go to nurse

Two humpback populations calve in the gulf in alternating seasons, and they come from opposite ends of the planet. The northern animals belong to the Central America population, listed endangered in the United States, one of only four humpback populations in the world to carry that listing; they feed off California, Oregon and Washington, swim some 5,100 kilometers south, and arrive from December to April, numbering only around 1,400. The southern animals migrate up from the feeding grounds off Chile and the Antarctic Peninsula and arrive from July to November. That southern stock was hunted to near-extinction by the early 1960s and has recovered strongly since the 1966 whaling ban; a 2006 estimate put it near 6,500, and more recent surveys put it far higher, roughly 12,000 by 2021 and about 27,000 in 2024. No other place on Earth hosts both, which is why researchers call the gulf a rare point of "potential trans-equatorial genetic exchange."

Alongside the whales live two small resident dolphin populations, present year-round: about 119 bottlenose and 368 pantropical spotted. Researchers counted them by photographing individual animals. The bottlenose keep inshore near the river mouths, where the females gather to nurse. The gulf's cetacean researchers have photographed individuals with fins sliced by propellers. The population also carries a chronic skin disease, first documented in 2014. In a resident group of just 119, a few boat strikes a year matter.

The humpback mothers and calves keep to the same water the boats use, and the mapping is precise. From years of survey records, David Herra-Miranda and colleagues at the Centro de Investigación de Cetáceos mapped the nursing pairs to the shallow inshore water. They cluster most densely along the western coast between Puerto Jiménez and Cabo Matapalo, with smaller mother-calf aggregations along the head of the gulf, from Punta Estrella toward the Esquinas River. The singing males and the groups of males competing for a female hold the deeper central water. The researchers read that split as the calving females moving inshore, away from the males in the sill. That shallow western coast is exactly where a marina is planned.

The biggest pressure on these whales is the warming ocean, more than the boats. The endangered northern herd has thinned across southern Costa Rica's Pacific since the mid-2010s, and the decline tracks that warming: across twenty years of survey effort off the Osa Peninsula, the breeding grounds the gulf sits within, encounters fell hardest in the long 2015-16 El Niño and correlate negatively with sea-surface temperature. In hot years the whales appear to stop short at intermediate latitudes off Mexico and Guatemala rather than complete the run to Costa Rica. Vessel rules cannot touch that. What they can do is protect the whales that keep coming.

A 2005 regulation governs how a vessel may approach a whale: slow, from behind, at an angle. A 2018 decree created an Area to Be Avoided at the gulf's mouth so that ships would route around the calving grounds, following the International Maritime Organization's collision guidance. But the 2018 decree bars only merchant vessels of 500 gross tons or more. Yachts, sport-fishing boats and tour pangas sit far below that line. The gulf has also been named an Important Marine Mammal Area by the IUCN's marine-mammal task force and a Whale Heritage Area by the World Cetacean Alliance, though neither designation binds a single boat. The alliance's own 2023 review found that the operators' self-policing "is not seen to be an effective way of managing negative impacts," and that no permit system limits how many boats work the whales. The approach rule tells a boat how to behave near a whale; it says nothing about how many boats may gather, where they may anchor, or how long they may stay. The traffic that concentrates in the calving strip is exactly what neither rule covers: the yachts that come in and anchor for weeks at a time, the sport and tour boats working the western coast. They are too small for the routing decree, and beyond the approach rule.

In the 1990s the paper company Stone Container planned a woodchip export port at Punta Estrella, a wharf for ships up to 70,000 tons fed by a timber trailer every four minutes, on a stretch of coast the whale researchers would later map as a mother-calf aggregation. Local ecologists and the gulf's communities fought it and beat it. An open-water tuna farm proposed around 2008 drew its own published assessment of the risk to cetaceans before it faded. The marina is the one that has not gone away. Filed at Puerto Jiménez in 2006 as Marina Bahía Cocodrilo, a basin of some 350 slips on the same water, it drew years of lawsuits its opponents lost. A 2016 study of the site judged the marina could negatively affect "the critical habitats of both local species," the gulf's bottlenose dolphins and its humpback whales, through increased traffic and noise. It was never shelved: the project is now advancing as Crocodile Bay Marina, the harbor of the Hilton-branded Botánika Osa Peninsula resort, with slips on the market as of 2026.

No one has yet published a measurement of vessel noise inside Golfo Dulce. The mechanism is established elsewhere: in controlled trials on resting humpback mothers in Australia, playback of vessel noise cut a mother's resting time by about a third and doubled her breathing rate. A nursing mother needs that rest.

Colombia has done what Costa Rica has not. Studying the same southern population at Gorgona, off its Pacific coast, researchers there recommended an official eight-month humpback season, May to December, with fishing and vessel traffic in the calving water held down to cut collisions and disturbance. Costa Rica routes the big ships around Golfo Dulce and tells the small ones how to approach a whale. It has set no such season, and nothing keeps the small boats out of the western shallows while the mothers are nursing there.

Reefs, and the pull the other way

A 2019 decree already bans coral extraction nationwide and orders a reef inventory. Restoration crews are replanting coral in the gulf now, Raising Coral Costa Rica among them, while groups like Innoceana monitor and study its reefs. A bill before the Assembly, expediente 25.013, sponsored by the independent deputy Kattia Cambronero, would oblige the environment ministry to inventory, monitor and restore coral reefs and seagrass beds; an environment committee approved it in February 2026 and sent it toward the floor. Pulling the other way is a separate push to reorganize the maritime-terrestrial zone, the public coastal strip the marine protections depend on, which critics read as a step toward privatizing the coast.

The forest reserve, the fishing area, the shark sanctuary, the routing decree, the coral law to come: each is a real protection, and most are barely enforced. The one that has held is the sanctuary the gulf's own fishers and scientists built and watch. The humpback mothers come in to the western shore to nurse, into the one stretch the State has closed to 500-ton ships but left open to every smaller boat, and the boats follow them in. Closing that gap would take a single, modest rule, a seasonal closure of that strip to small-boat traffic, the kind researchers urged for these same whales at Gorgona. The people who built the sanctuary could build that rule too.