Just before dawn along the banks of Burma’s Irrawaddy River, local fisher Maung Lay sits at the bow of his boat tapping portside with a bamboo stick, straining his eyes for any movement in the still water.

Within a few minutes, a dolphin breaks the glossy surface and exhales a plume of mist. Maung Lay stands with his net over his shoulder and purrs loudly toward the river. This is his call for help.

“They’re coming,” he says.

Several more dolphins arrive, breaching closer to the boat, ready to drive fish into Maung Lay’s net in exchange for a share of the catch. But despite casting net after net, not a fish could be found. “There were electrofishermen here last night,” Maung Lay says. “They have killed all the fish in this area.”

Fish are becoming harder to find all over the Irrawaddy River, in part because electrofishing gangs are rapidly depleting the already strained stocks of more than 40 local species. The relatively recent practice of electrofishing sends electric currents into the water through metal rods or conductive nets that are connected to car batteries, stunning fish in groups and making for an easy haul.

This increasingly ubiquitous but illegal practice is disrupting the food source for the at-risk river dolphins. Local conservationists also suspect electrofishing accidentally killed at least two dolphins last year.

Every loss is keenly felt: The International Union for the Conservation of Nature lists the Irrawaddy dolphin as vulnerable. While the species lives along coastlines, deltas and estuaries from the Bay of Bengal to the Philippines, as well as in other rivers including the Mekong and Ganges, the Burmese population is critically endangered—today fewer than 60 dolphins remain in the Irrawaddy.

And with fewer dolphins chasing fewer fish, the centuries-old cooperative relationship between humans and dolphins is also facing extinction.

It’s not entirely clear how long fishers in Burma have had a partnership with the dolphins, but the animals are part of local lore. The practice is mentioned in a natural history journal from 1871, suggesting cooperative fishing goes back at least that far. Today more than 100 households along the Irrawaddy fish with help from the dolphins.

Maung Lay learned how to call them from his father, and he has worked with them for more than 30 years. A 2007 study from the Wildlife Conservation Society (WCS) noted that fishers could haul in a catch of 60 pounds with help from the dolphins, compared to 11 pounds without them.

“Irrawaddy dolphins are generally revered by local people in Myanmar, and they provide direct economic benefits to cast-net fishermen via their role in a human-dolphin cooperative fishery,” says Maung Maung Aye of the University of Yangon.

But the river’s fish stocks began to plummet ten years ago, right about the time when electrofishing became popular, according to Kyaw Hla Thein, a deputy project manager at the WCS in Burma. Techniques have shifted since then from small electric rods to more sophisticated nets lined with copper that are able to stun and collect more fish.

Other activities upstream on the Irrawaddy River also harm the fish: Logging, dredging, agricultural runoff and gold mining all lead to habitat degradation. While the government has attempted to crack down on logging and mining in recent years, electrofishing is more difficult to stamp out.

In 2005, WCS and Burma's Department of Fisheries established a protected zone on a 40-mile stretch of the river north of Mandalay. Gillnets and dragnets that can be harmful to the dolphins were banned, as well as catching, killing or trading in dolphins.

The government set a three-year prison sentence for anyone caught electrofishing, and the Department of Fisheries, local police and WCS officials share patrolling duties. But electrofishers often react violently, and they can easily outrun patrol boats.

“On every survey trip we see electrofishing boats,” says Kyaw Hla Thein. “They run away when they see us.”

Compounding the problem, the government sells commercial fishing contracts as competitive bids, which can lead to unsustainable plundering of the Irrawaddy River, says Han Win, a dolphin expert at Burma’s Fisheries Department. The concessions create incentive to collect as many fish as possible—no matter the technique.

“In the dolphin protected area, according to interviews with fishermen and data collected, we found that fish catch of small scale fishermen declined 50 percent compared with the last 5 years,” says Han Win. “We need other related departments and organizations to cooperate in controlling and eradicating electric fishing, such as the police stations and courts.”

In the meantime, WCS is developing eco-tours along the Irrawaddy, in the hope that Burma's waves of wealthy tourists can help create incentive to protect the dolphins and their habitat. At least six tours have already been launched.

While Maung Lay waits to see if ecotourism and stepped-up policing will help, he can only continue to fish. The sun sits low over the Irrawaddy after another unsuccessful day on the river. Maung Lay pulls some twigs and a small dead fish from his net.

“Electrofishers have no relationship with the dolphins,” he says. “When they electrofish, they kill fish, and the dolphins will not eat dead fish. The electrofishers don’t think about the dolphin, because they only want profits.”

Maung Lay turns back to the river, taps his bamboo stick and purrs, holding out hope for a catch. But this time, no dolphins are around to greet him.