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A marine mammal is on the verge of extinction in Mexico's Gulf of California. Conservationists have been trying to save the vaquita porpoise for years, but that work has been complicated by illegal nets and even drug cartels. From Arizona Public Media in Tucson, Ariana Brocious reports.

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ARIANA BROCIOUS, BYLINE: Seafood restaurants and colorful mosaics line the boardwalk in downtown San Felipe. Fishing is a mainstay of this small northern Mexico town. La Vaquita restaurant is just a couple blocks over. A framed photo of the little porpoise that could be the town's mascot hangs in the office of Ramon Franco Diaz (ph), head of a local fisherman co-operative representing about 570 families.

RAMON FRANCO DIAZ: (Through interpreter) That animal, as you must know, only lives here in this area, and it's ours. It belongs to us Mexicans.

BROCIOUS: For decades, the vaquita's population has been declining as fishermen inadvertently catch them while pursuing fish and shrimp. But Diaz says many local fishermen treasure the animal. When it rises above the water with its characteristic black-rimmed eyes, he says...

DIAZ: (Through interpreter) It's as if it was smiling with you. So real fishermen don't want to harm them. It's the opposite.

BROCIOUS: In the last few decades, Mexico has established a vaquita refuge and backed research into the species. But lately, the number of vaquita has plummeted to around just a dozen or less as poaching for another endangered fish, called the totoaba, has ramped up. Fishermen use large gill nets to trap the totoaba, which also kill vaquita. In 2015, Mexico's then-president banned gill nets in the vaquita's habitat, increased enforcement against poaching and started paying fishermen not to work so the species could recover.

DIAZ: (Through interpreter) So we came to an agreement that we would leave the sea so that the federal government could clean up the illegal boats.

BROCIOUS: But Diaz says enforcement was insufficient, and the problem got worse. He says he's filed numerous complaints with the government to no avail. Then, a year ago, the payments to fishermen stopped.

DIAZ: (Through interpreter) So now we have a serious problem because we don't have a fishing practice that is permitted and we also don't have any compensation.

BROCIOUS: Last September, Diaz announced his fishermen had no option but to return to the sea to support their families. He says a 2018 U.S. ban on Mexican seafood caught with gill nets has only made life harder for legal fishermen.

BARBARA TAYLOR: Mexico missed an opportunity to be a world leader in shifting a fishery over from gill nets to alternative gear.

BROCIOUS: Barbara Taylor is a marine conservation biologist with the U.S. government who has studied the vaquita for 30 years. She says the gill net ban wasn't very effective because some fishermen, hurting financially, were tempted into the illegal totoaba trade.

TAYLOR: Vaquitas and gill nets are completely incompatible, and the fishermen needed to be able to make a living. And so developing alternative fishing methods were really the only way for vaquitas to survive.

BROCIOUS: Luis Albanel (ph) Mendoza is working on it. In his San Felipe office, he pulls a large, thin strand of net from a milk crate.

LUIS ALBANEZ MENDOZA: This is the weight. These go to the bottom.

BROCIOUS: He's a member of Pesca ABC, a small nonprofit group of fishermen working with the Mexican government to test alternative drift nets like this one, called a suripera.

ALBANEZ MENDOZA: It's vaquita-safe. This work with the current, only with the current.

BROCIOUS: But Mendoza says using these nets can be nearly impossible because of the sheer number of illegal gill nets under the waves. He says even though it's cheaper, it will be hard to convince fishermen to use it.

ALBANEZ MENDOZA: They don't want to fish because it's very effective, you know, the gill nets. And with this kind of equipment, you have problems to get money.

BROCIOUS: Vaquita researcher Barbara Taylor says Mexico needs to support legal fishing if alternative nets prove less profitable and crack down on poaching in the vaquita's prime habitat. She still has hope for the species, but there are fewer vaquita every year. Totoaba poaching is rampant because the fish's swim bladder is highly prized in China as a medicinal food.

JP GEOFFROY: Because it's a lot of money. It's more money than drugs. I mean, we're talking about $20,000, $25,000 for one swim bladder.

BROCIOUS: J.P. Geoffroy leads the conservation group Sea Shepherd's vaquita protection efforts. He says that money has attracted international drug cartels, and during high season, there can be dozens of boats fishing illegally inside the vaquita refuge. For the last five years, Sea Shepherd has been working with some local fishermen to collect gill nets, trying to give the species a fighting chance to recover.

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BROCIOUS: In port in San Felipe, crew members use a hook to move huge bags of fishing gear they've pulled from the ocean.

GEOFFROY: All these bags contain all the illegal nets that we removed from the refuge of the vaquita.

BROCIOUS: Not all locals support Sea Shepherd's work. Recently, suspected poachers fired shots at a Sea Shepherd vessel in the vaquita refuge. Despite that tension, Geoffroy says they support local fishermen who just want to do their job.

GEOFFROY: We are just trying to work with them and explain to them to at least respect the small rectangle that is the critical area.

BROCIOUS: Geoffroy says if they can just protect the remaining vaquita, the species can recover, but for now observers say there's little evidence that current efforts to stop poaching will be enough. For NPR News, I'm Ariana Brocious. Transcript provided by NPR, Copyright NPR.