A new agreement hopes to save the world's rarest cetacean from extinction. But whether it will work on the ground remains to be seen, experts caution.

The agreement signed Wednesday by the government of Mexico, the Leonardo DiCaprio Foundation, and the Carlos Slim Foundation supports emergency measures to conserve the critically endangered vaquita, which is threatened in the Upper Gulf of California as a result of fishing bycatch.

The agreement includes a permanent ban on gillnets, in addition to the retrieval of all abandoned “ghost” nets within vaquita habitat. Gillnetting, a vertical netting method used by fishermen, causes vaquitas to become entangled and often drown (even though they aren't being targeted by the fishermen), and discarded nets remain a continued threat to marine life.

The deal also includes support for the development of new fishing gear and techniques that would allow local communities to resume fishing—but with less risk to vaquitas.

The vaquita porpoise—also known as the “panda of the sea” for its distinctive markings—is on the brink of extinction with some 30 remaining and can only be found in the Gulf of California (also called the Sea of Cortez). The porpoises get caught in nets primarily as fishermen seek the Totoaba macdonaldi fish, also an endangered species, and one that can't be hunted legally.

But a catch of totoaba can bring in $20,000 or more on the black market. It is considered an anti-aging cure-all in parts of Asia and is illegally traded in the United States, Mexico, and China.

Actor and environmental activist Leonardo DiCaprio called for action from Mexican president Enrique Pena Nieto on the matter last month. Nieto responded on Twitter, promising that Mexico was committed to protecting the vaquita, as well as other endangered species.

Shortly after that, Mexico's government created a plan to locate and capture surviving vaquitas in order to move them to a marine sanctuary in the Sea of Cortez, where experts will help them reproduce. (Read "Three Nations Create Giant Reserves for Ocean Life")

This week, DiCaprio and Nieto met with Mexico’s richest man, Carlos Slim, to sign a memorandum of understanding to protect the vaquita porpoises from extinction and assist fishermen in becoming more sustainable.

“We have implemented a historic effort to avoid the extinction of a unique species, the vaquita marina, and to protect our ecosystem,” Nieto wrote in a statement posted on Twitter.

The World Wildlife Fund (WWF) has spent the last 10 years working with the Mexican government and local fishermen in the Upper Gulf to provide alternative fishing resources, says Jorge Rickards, acting director of WWF-Mexico. (Read "Saving the World's Oceans is This Marine Biologist's Life Pursuit")

With the new agreement in place, Rickards said WWF is now calling on the Mexican government to help fishermen transition to better gear before the next fishing season begins in a few months.

“My opinion is that the government could have moved a lot faster to implement these alternatives and develop new ones, as well,” Rickards said. “Unfortunately, now, we are in a very complex moment in which we have less than 30 vaquitas left.

“The communities are unsure if alternative [gear is] going to cover their needs,” Rickards adds. Getting buy-in from the local fishing community is essential if the vaquita has any long-term prospects in the wild, he says.

Some fishermen in Mexico are already fighting the gear bans, saying it puts their livelihood at risk.

“There is a group of fishermen that are totally convinced of the transition, but not all fisherman are,” Rickards said. “I think the challenge the government has right now is to convince fishermen to use the alternatives that have been approved and provide other means of livelihood.”

Other environmental issues in the region also need to be addressed, such as pollution, he added. (Read "This Small Island Nation Makes a Big Case For Protecting Our Oceans")

The ripple effects of losing even one species can be detrimental to the marine ecosystem, but humans are at risk, too, says marine biologist Silvia Earle in next week’s episode of Explorer, which investigates illegal fishing in the Sea of Cortez:

“We are totally connected to everything else, and what we do to the ocean, what we do to nature, we’re doing to our future, to our life support system. We may cause ourselves to go extinct because we’ve altered the nature of nature.”

“This is not a problem only unique to Mexico; this is a problem that we find in many places, and not only marine ecosystems,” Rickards said. “If we lose vaquitas, it would mean failure of so many years of work, and it would force us to rethink many of the approaches that government and civil society and local communities have taken to address these issues and others like them around the world.”

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