Dolphins and Humans Cooperate To Catch Fish

The state of the universe.
Jan. 31 2013 1:41 PM

Fishing With Dolphins

An astonishing cooperative venture in which every species wins but the fish.

Dolphins and fishermen work together in Laguna, Brazil, to catch groups of mullet.
Dolphins and fishermen work together in Laguna, Brazil, to catch mullet.

Photo courtesy of Fábio Daura-Jorge

The road to Laguna is lined with gossamer. Nylon nets hang from wooden posts and eucalyptus trees, weighed down by lead sinkers. The synthetic fabric may be new, but the design is ancient: Hand-cast nets have been found in Egyptian tombs and are mentioned in the New Testament. Such fishing nets were likely introduced to this area of southeastern Brazil by immigrants from the Azores, perhaps in the 16th century.

Laguna is really two cities. The old colonial town fans out on the eponymous lagoon, with brightly colored buildings and blue-and-white azulejo tiles adorning some of the homes. Then there’s the new, rather charmless city that has taken over the ocean side, its glass and steel spines like the shell of a sea urchin. To the south is a sliver of land that points into the Atlantic Ocean, with a small beach called Tesoura. Here, an extraordinary relationship has evolved between fishermen and animals that are often seen as competitors. It was announced by a signpost: Observação de Botos (Dolphin Watching).

Early on the morning I showed up, men were arriving on bicycles, red or green milk crates holding their nylon nets. They were deeply tanned, some in shorts, some in waders. Ivan Ferraz de Bem, in a wetsuit stretched over an ample beer belly, took a cast net out of his red dune buggy. A skull-and-crossbones flag tied to his bumper snapped in the stiff wind. Recently retired from a government job in Brasilia, he seemed to enjoy the hours by the shore––and those in the nearby bar to which he retreated when things slowed down even more.

As we watched the turbid green waters flow into the lagoon, a tall dorsal fin broke the surface, followed by a smaller one. A mother dolphin and calf swam in, the youngster staying close to its parent’s side, then headed out for rougher waters. Perhaps they found no fish or were just assessing the situation. These are wild dolphins—untrained, undomesticated—and it was clear that they run the show. When the dolphins aren’t around, one fisherman told me, it’s not worth fishing. Some gave it a try anyway, with an underhand toss into the blue. A few small fish were landed.

Another dorsal fin rose a hundred meters from the shore. “Escubi,” one man called out, recognizing the white scuff marks on the leading edge of the fin. The men broke off their chatter, dashed into the water. Thigh deep, almost motionless, they stood at the ready, a line of six, as if awaiting Escubi’s orders.

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Most of the helpful dolphins have names: “Escubi” is a variant of Scooby Doo. “Filipe” is a Brazilian adaptation of Flipper. Dolphins have something like names among themselves, too—each has a signature whistle, and they recognize one another by their unique calls when they meet at sea.

Another blow broke the surface. Escubi lifted his dorsal fin, reversed course. One man splashed his net in the water, to convey where he was standing. Escubi signaled with a slap of his gray tail, then charged straight for the shore.

Dolphins can swim faster and accelerate more quickly than torpedoes, so the nearest fisherman, in an olive green rain jacket and black cap, cast his net quickly as Escubi approached. It spread like a spider web, landed on the surface, and closed below as Escubi veered to the left. As the fisherman retrieved the hand line, a large tainha, the local mullet, thrashed in the mesh.

Escubi headed out to sea. The men cleaned their fish. One tossed an anchovy to a razor-thin heron, feathers lifting like white caps in the wind.

On coastlines around the world, many fishermen see dolphins and other marine mammals as competitors or thieves, often to be shot on sight. Soon after I left Laguna, a bottlenose dolphin was found dead in Louisiana, shot to death just behind its blowhole. It was the sixth killing recorded in the area this year. A dolphin in Alabama had been stabbed in the head with a screwdriver. One had its tail cut off and somehow survived. Many Hawaiian dolphins have bullet wounds in their dorsal fins, and entire groups are shy around people, even avoiding research boats, apparently having learned to fear that the people might be armed.

Here in Laguna, things are different. Cooperative fishing has been going on for at least 120 years—there’s reference to it in a 19th century letter—but no one knows how it started. Did a few dolphins curiously approach a couple of fishermen one day, flashing their dorsal fins or slapping their crescent-moon-shaped tails, and discover a new way to outsmart the speedy tainha? Since dolphins are considered net thieves in much of the world, did men try to chase them off at first? How did the dolphins convince the humans that they could be of service? Who trained whom, and when? One archeologist is looking among the sambaquis, or native middens, for evidence that the relationship between dolphins and humans may have existed even before the Azoreans arrived.

What’s in it for the dolphin? No one can say for sure. Paulo Simões-Lopes, a professor at the Federal University of Santa Catarina who has been studying this population for more than 20 years, hypothesizes that the cooperative fishing disorients and isolates the fish. As the fishermen cast their nets, the school panics, and the dolphins exploit the chaos. They catch larger, quicker fish that would be difficult to capture in a straight-out chase.

Most of the dolphins in the region are residents. A few are vagabonds, traveling up and down the coastline. They have spread the cooperative tradition to a community about 150 miles to the south. Of the 55 resident dolphins identified in the area, 21 cooperate with fishermen; the rest generally don't. About 200 fishermen take their cues from the botos bons, or “good” dolphins. Those that keep to themselves are described as botos ruins, “bad” dolphins.

Most of the fishermen are part-timers, spending a few hours here before returning to their day jobs. One told me, “You can’t live on fish alone.”

Many are deeply tanned, relishing their time at the shore. “Everything's computerized,” another complained. “I detest computers.”

Ferraz de Bem says that he likes computers—we exchange Facebook info—but why browse the day away? A few spend the entire day here, fishing and gabbing: Pensioners, like de Bem, have all kinds of time.

Fishing here depends in part on the tides, but mostly it follows the dolphins and their biosonar, their ability to use echoes to navigate and hunt. The water is too turbid to see much below the surface.

Simões-Lopes has shown statistically what these fishermen already know: When they fish cooperatively with dolphins, they have more fishing opportunities (the frequency of casts per hour is higher), and they land more fish. And the fish they do bring ashore—mostly mullet in winter, anchovies in summer—are larger.

In the 20th century, humans trained thousands of dolphins. They taught them to “walk” backward in aquariums in the manner of Flipper, to be brushed and fondled in theme parks, and to detect underwater explosives for the military. For a while during the Cold War, it was thought that dolphins could even attach warheads to enemy submarines, though it is likely that the U.S. Navy’s chief interest in dolphins was in how to learn from their extraordinary powers of propulsion. The Navy released a propaganda film with “a perfectly fantastic ‘Human-Dolphin Translator,’ ” the Princeton historian of science D. Graham Burnett has written. “And (I could not make this up) the Navy scientists ultimately decided to try speaking to them in Hawaiian, on the grounds that this language seemed likely to be closest to their own.” (It being the 1960s, some saw this as preparation for communicating with extraterrestrials.) The Navy is set to phase out its sea mammal program beginning in 2017, the mine-hunting dolphins to be replaced by underwater drones.