Dolphins are a man’s best friend in Santa Catarina

The names Juscelino, Figueiredo, and Tancredo are those of former Brazilian presidents of note. The first founded the capital Brasília, the second began the process of easing and opening the 1964-1985 military dictatorship, and the third was the first democratically elected president post-dictatorship, although he died before taking office. 

But for the residents of Laguna, a coastal city in the southern state of Santa Catarina, those names more readily recall local bottlenose dolphins than the deceased former heads of state. 

That is because in Laguna, the dolphins herd fish and collaborate directly with fishing, the city’s main economic activity. In fact, they are considered employees, just like local fishermen.

While “herding” may sound odd when talking about aquatic animals, that’s exactly what the bottlenose dolphins do. Like dogs guiding sheep, they “push” shoals of mullet into the cast nets used by artisanal fishermen. Positioned in the sea or on a pier, fishermen await a sign from the dolphins, who, after finding and surrounding the mullets, emit an acoustic signal (like an underwater shout) and make vigorous movements to get the fishermen’s attention, who then know that it is time to cast their nets. 

The mullet is cornered in such a way that the fish either get tangled up in the net or swim into the mouth of the dolphins. For the fishing to be most effective, there must be exactly seven seconds between the dolphin’s signal and the throwing of the net.

When the movements are synchronized, the fishermen catch four times more fish than without the help of the dolphins. The aquatic mammals, in turn, are 13 percent more likely to survive from one year to the next when they collaborate with human fishery.

Researchers have been studying this rare phenomenon of cooperation since the 1980s, with only two other similar cases in the world, in Myanmar and India. But it is only in recent years that technology has made it possible to collect and analyze data underwater. Since 2018, drones, cameras, and microphones have been set up in the bay of Lagoa Santo Antônio dos Anjos, in Laguna, to record movements in and out...