In Laguna, Brazil, fishermen and dolphins have worked side by side for more than a century. Now researchers have uncovered how it happened.
Laguna – Normally, dolphins are severely threatened by human fishing. Again and again they end up as by-catch in the fishermen’s net and die there. There is even talk of dolphin content in tuna products. But as we all know, exceptions make the rule. In fact, in the Brazilian Laguna, dolphins and fishermen work closely together – and have done so for over a century. Now researchers have decoded the special relationship between humans and animals and why both sides benefit from it.
Dolphins drive schools of fish close to shore – so anglers can cast their nets
The spectacle can be seen in a video YouTube to be observed. This shows how the dolphins would attempt to herd schools of fish, particularly mullet, close to shore. They would then signal the fishermen where to cast their nets to catch as many fish as possible.
The dolphins would use their so-called echolocation to assess the fish population around them. When enough prey was around, the dolphins would arch their backs or slap their fins on the water to send a signal to humans. Then Laguna’s anglers cast their circular nets to scoop the bundled school of fish out of the water.
Dolphins live longer when they cooperate with humans, study says
Now researchers at Oregon State University have found out why the dolphins behave the way they do. In a study the science team said the partnership would benefit the dolphins because they live longer, on average, when cooperating with humans. Because it is much easier for the dolphins to chase a few fish out of the net than in the wild.
“The dolphins are really good at herding mullets,” explains Mauricio Cantor, an assistant professor at Oregon State University’s College of Agricultural Sciences and author of the study insider. They know how to “get a school of fish really tight and compact” before they herd the fish towards the fisherman. However, since mullets are difficult for dolphins to catch when swimming in a compact school, they rely on human nets.
Dolphins threatened by industrial fishing
Without the dolphins, the fishing method wouldn’t work: “The water’s super murky, so you can’t see where the fish are, but you can see where the dolphins are,” Cantor says. After the signal from the dolphins, the fishermen had about seven seconds to cast the net.
When the dolphins were satisfied with the throw, they would emit a loud echolocation click. “We can hear it, it sounds like a door creaking,” Cantor said. “The other non-cooperative dolphins spend most of their time foraging, where they encounter all kinds of other fisheries, including illegal fisheries,” the researcher explains. That’s why animal rights activists keep protesting against dolphin deaths. “These dolphins are more likely to get caught in the long trawls that kill anything they touch.” last is Fishermen even accidentally caught a sunfish in their nets.
Laguna dolphins live 13 percent longer – because they work with humans
According to the study, lagoon dolphins live 13 percent longer than other dolphins. In addition, some dolphins travel more than 200 kilometers a day, mainly for hunting. Dolphins from the Laguna coast, on the other hand, would live in the fishermen’s area all the time. These are around 50 to 60 copies.
‘Will lose interest’: Human-dolphin cooperation under threat
But now the symbiosis between humans and dolphins is also threatened in Laguna. Cantor explains, “Fish are becoming increasingly scarce, partly due to illegal fishing. People are also moving away from fishing as their main source of income”. As a result, more and more people are just doing this practice as a hobby, losing “some of the precision when it comes to when to cast the nets,” Cantor says.
He goes on to explain, “Dolphins are smart and will lose interest when they see that they are not getting the benefits they used to have from working together.” It’s complicated because “we need the dolphins, we need the fish, we need the fishermen, but we also need that subtle knowledge of how to interact,” he said. “Of course, if they don’t practice every day, they’re not as experienced or as skilled as the others.”
A spectacular one Underwater video now shows a tuna running away from a shark.
#Fishermen #follow #instructions #wild #dolphins