(CNN)Deep in the Pacific Ocean, an underwater "superhighway" stretches roughly 700 kilometers (430 miles) between the marine reserves of Ecuador's Galapagos Islands and Cocos Island, off the coast of Costa Rica.
It's vital to the sea life -- including sea turtles, whale sharks and hammerhead sharks -- that moves back and forth between the islands, looking for a place to nest or foraging for food.
But the route can be dangerous. Unlike the marine reserves at each end, the swimway is open to fishing vessels. Data shows that populations of migratory species, many of which are already endangered, are declining.
Schools of hammerhead sharks migrate along the swimway. (Courtesy Alex Hearn)
Protecting biodiversity hotspots around the islands is not enough, says Alex Hearn, biology professor and founding member of MigraMar, a coalition of scientists and environmental groups. His team is campaigning for the entire swimway to be protected -- an area that would stretch over 240,000 square kilometres (93,000 square miles) of ocean, about the size of the United Kingdom.
This would extend fishing restrictions beyond the current 22-kilometer radius around Cocos Island and the 74-kilometer radius around the Galapagos islands, creating a narrow protected channel between the two that follows a chain of seamounts, underwater mountains that rise from the sea floor.
Like landmarks for the ocean, the seamounts are vital for navigation. Made from lava, they emit magnetic signals, which some species, such as hammerhead sharks and sea turtles, rely on to locate themselves, explains Hearn. He says these act as "stepping stones," providing places for sea creatures to feed and rest during migration.
A game of tag
For more than a decade, MigraMar's network of scientists have been trying to prove the importance of the swimway by documenting the species that use it. They have placed satellite and ultrasonic tags on almost 400 marine organisms to track their migratory routes.
So far, they have successfully tracked the migration of whale sharks, hammerhead sharks, silky sharks, leatherback turtles and green turtles between the two islands. And in February, for the first time, they discovered evidence of tiger sharks, when a nine-foot-long female tiger shark scientists had tagged in the Galapagos seven years ago surfaced at Cocos Island.
All of these species are suffering from population decline and are listed as vulnerable, endangered or critically endangered, except the tiger shark which is considered near threatened. As tiger sharks are one of the top predators in the Pacific, it is vital to protect their migratory pathway, says Todd Steiner, executive director of Turtle Island Restoration Network and another founding member of MigraMar.
"The impact of tiger sharks is felt all the way down the food chain," he tells CNN. "Having a healthy ecosystem where tiger sharks survive is important."
The most common threat to these migratory species is fishing. They can be accidentally caught by fishing vessels, entangle themselves in nets, or in the case of sharks, are illegally hunted for their meat and fins.
Compared to other threats they face, such as climate change, fishing is easier for us to control, says Steiner.
Coastal countries can restrict activities in their territorial waters, he explains, and the Cocos-Galapagos swimway falls under the jurisdiction of both Ecuador and Costa Rica. "A couple of signatures on a piece of paper can start the process to protect this vitally important ecological area," he says.
MigraMar and environmental organization Pacifico have produced a document outlining the need to create the swimway, calling for it to include "no take zones" that prohibit human disturbance such as fishing or dredging, or management zones where only sustainable and seasonal fishing is permitted.
Carlos Chacón, coordinator of Pacífico, says that finding "common ground" with the fishing sector will be crucial in ratifying the swimway as a marine protected area (MPA). The proposal has already been met with resistance from the fishing industry in both countries, he says, who claim it would have a negative impact on business.
Atunec, the Ecuadorian Tuna Boat Association, opposed a different proposal to expand the Galapagos marine reserve last year, saying that the area is very rich in fishing and creating a no-take zone would reduce its catch.
However, Chacón believes that in the long term marine protected areas will have a positive impact on fishing. "MPAs become nurseries," he says, where fish grow and reproduce, causing overall stocks to increase and more fish to become available outside the protected area.
It could also have economic benefits in other sectors. Cocos and the Galapagos attract visitors thanks to their rich biodiversity and preserving iconic sea life could protect the tourism sector.
Time is short
Ecuador and Costa Rica are currently considering plans to protect the swimway, with MigraMar's data being used to inform their decisions.
Both nations have signed up to the Global Ocean Alliance, a UK-led initiative that calls for 30% of the ocean to be protected by 2030. This shows political will, says Steiner, but with only 13% of Ecuador's and 3% of Costa Rica's waters safeguarded so far, the countries need to convert this will into action.
Closing off the swimway to fishing fleets could help protect endangered hammerhead sharks. (Courtesy Cesar Peñaherrera)
Costa Rica is currently "implementing a strategy to increase conservation, especially by creating and strengthening marine protected areas," Haydée Rodríguez Romero, the government's vice minister for water and the ocean, tells CNN. This will involve increasing conservation around Cocos Island, she says, adding that "we acknowledge the importance of protecting the swimways."
While the government of Ecuador did not respond to CNN's request for comment by the time of publication, it has been reported that it is looking at extending the Galapagos Marine Reserve, which would cover the entire Ecuadorian side of the swimway. Rodríguez Romero says that the two countries are in discussion over marine protected areas and law enforcement in the ocean.
"Momentum is building, and the science is clear," says Steiner. "We're hopeful that action will be taken in the near future." But he warns that with some species under threat of extinction, governments need to act fast.
"We've taken baby steps," he says, "but these endangered species don't have time for that."