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.

Advertisement

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.

No matter how pedestrian, cynical, or out-there the goals were, the transactions were largely performed in captivity, with dead fish as currency. Some researchers may have considered dolphins capable of conversation, dreaming of the day when the animals could visit and leave the labs as they wished, but in practice the relationship differed little from that of people and their dogs or any other clever domestic animal.

Here on the small beaches of Laguna, no fish are exchanged directly. The dolphins work on their own time: The fishermen often stand idly onshore when the botos are not around. “There is no schedule here,” a fisherman told me. “Sem botos, não da.” (Without dolphins, it’s not worth it.)       

Beyond Brazil, such symbiotic interactions, in which both humans and a wild species benefit, are rare. Most appear to be what biologists call commensal relationships: One side benefits, the other neither gains nor loses. (Dolphins feeding on fisheries discards is a good example of commensalism.) When dolphins feed directly off of a fishing line, it’s known as parasitism, or kleptoparasitism, and it often fuels tensions between fisheries and cetaceans. But in Burma, the Irrawaddy dolphins appear to cooperate with a cast-net fishery, and there are accounts of Australian aborigines fishing with dolphins and orcas in eastern Australia. In Mauritania, dolphins help strand mullet on the beach, in what has been described as a “great melee.”

Simões-Lopes believes that a similar process occurs in the relaxed atmosphere of Laguna. The techniques and rewards of cooperative feeding are passed from generation to generation—by the fishermen, as well as the dolphins. “When the kids come, they learn,” a fisherman told me, talking about the juvenile dolphins. Mother dolphins train their offspring by escorting them toward the nets and then letting the young give chase.

Daura-Jorge describes the social structure of the good dolphins as “fission-fusion:” a fluid social network dominated by short-term associations that often form around the fishermen, then break apart.

That night, I stopped by a restaurant across the street from my lodgings (the Flipper Hotel, of course). The place was nearly empty. The menu was long, but there it was: grilled tainha. Mullet isn’t my favorite fish, but I couldn’t find a good excuse not to order it.

A tainha the length of my forearm arrived, sizzling on a hotplate. It was moist, fresh, and delicious. This being Brazil, it was accompanied by french fries, rice, a salad, and pirão, a thick orange fish sauce. When the waiter returned with a beer, I asked him where the fish was from. “Tesoura.” Mine was a dolphin-assisted meal.

Tesoura seems like a throwback in time, before fishing became industrial, from some time in our distant past, if it ever existed, when there was a pervading sense of harmony. The fishermen have a tradition of cooperation with the dolphins and among themselves: Simões-Lopes has recorded a “shift rotation system” that prevents one fisherman from taking more than his fair share. At Tesoura, when a man catches two mullets, he has to leave his place in the water, which is taken by the next one in line. Elsewhere in Laguna, the person who gets a fish big enough to feed his family has to yield his place to the next.

That morning, the men fed small fish to the cats. They pet the stray dogs. They tossed the occasional fish to the herons waiting patiently on the edge of the riprap. They told me a story about an endangered right whale that swam up the channel with its newborn calf a couple of years ago. The pair became disoriented in the lagoon, and after showing signs of distress, the whales were joined by a few dolphins. Though much smaller even than the newborn whale, the dolphins escorted the mother and calf out of the channel to the safety of the open sea. Or so the fishermen say.

As the sun goes down, Laguna can feel dreamlike, almost Edenic. But I’m from a family of worriers, so I worry. As I sat on the shore, I started to think about the risks of disease transmission. Most of the dog and cat feces must wash into the sea. Toxoplasma, a parasitic protozoan carried by cats, has been found in seals and sea otters, giardia in whales.

The fishermen look out for the dolphins. Daura-Jorge told me that he couldn’t biopsy them, which required taking a piece of skin and blubber the size of a pencil eraser, within sight of Tesoura. The fishermen got too upset. But bigger risks waited up in the lagoon. Dolphins occasionally swim into gill nets stretched along the Tubarão River that flows into the lagoon; they get entangled and often die. (The “good” dolphins have a slightly higher mortality rate.)

Changes in the fishery may be putting the relationship between fishermen and dolphins at risk. The last season has been pretty bad for the mullet fishermen of Santa Catarina. Some locals blame fishermen from Uruguay for endangering the fish population by targeting gravid females for the roe. (When I looked, mullet roe, or bottarga, was available on-line from Uruguay and Brazil in 50-pound cartons. External markets, whether in Japan, Europe, or elsewhere, can tilt the balance of local fisheries away from sustainability.) Daura-Jorge isn’t so sure the pressure is external: 2011 was one of the best years that anyone could remember for cooperative hunting, and 2012 was one of the worst. The bad year could be a blip, or something more worrisome. Natural resource managers use the term “killer spike,” to describe a pattern of rising catches, followed by a steep decline.

Given the ravages that we have imposed on the ocean, I admit to feeling reluctant to celebrate any aid in removing fish from the sea. Are these dolphins helping build a sustainable coastal economy, or are they helping destroy it?

There is resilience to this dolphin population. Cooperative fishing survived the 1940s construction of the kilometer-long jetty that points out into the South Atlantic. The jetty changed the hydrology of the region—the lagoon, once only intermittently connected to the ocean, is now permanently linked by a channel. Still, the inlet is rarely used. During the few windy days I stayed in Laguna, I never saw a boat head out to sea. The waters at the mouth are often too rough for navigation.

The dolphins have no such troubles. When most of the men started packing up for the day, a mother-calf pair left Laguna, headed east to the open ocean. I followed the dolphins out to the point. These are wild animals, at home in the rough sea, which almost lapped against the pink ceramic lighthouse. If the snarling whitecaps bothered the mother-calf pair, I couldn't see it. They seemed to be enjoying the breakers, intentionally choosing the roughest patches to surf, swimming to the back of the wave, and then breaking through the crest.

A wave heaved up over the jetty, soaking my pants. As I hustled back to town, I noticed that a fisherman had returned to Tesoura. A dark triangle slowly approached him from the water. It was getting oddly close and wasn’t submerging like a dolphin. I wondered if it was a shark, or perhaps a dog.

But no. It was another “enemy” of the fisherman, the sea lion. In many parts of the world, a fisherman would shoot a pinniped on sight (or out of sight, if the animal was protected by law). The seal paused, nose in the air, head slightly tilted, then approached the fisherman, who slapped his thigh, as if calling in a new tradition.

Joe Roman is a conservation biologist at the University of Vermont and a fellow at the Gund Institute for Ecological Economics. He is the author of Listed: Dispatches from America's Endangered Species Act, winner of the 2011 Rachel Carson Environment Book Award. His website is www.joeroman.com. This article was written while he was a Fulbright Scholar in Brazil.

  Slate Plus
Slate Picks
Dec. 19 2014 4:15 PM What Happened at Slate This Week? Staff writer Lily Hay Newman shares what stories intrigued her at the magazine this week.