Humans and dolphins on Brazil's southern coast create a beautiful synchronized "dance" to guide the path of many migrating mullet into their nets and mouths.
Traditional fishermen in Laguna City have been working with Lahill's bottlenose dolphins (Tursiops truncatus gephyreus) for more than 140 years.
From above, dolphins appear to lead schools of mullet to shore, near fishermen wading in the shallows. Only after receiving a signal from the dolphins, the fishermen cast their nets.
Researchers have spent more than a decade studying this close relationship. They say it is a rare example of mutualism, in which two species help each other improve their chances of survival.
“We knew that the fishermen were watching the behavior of the dolphins to determine when to cast their nets, but we didn't know if the dolphins were coordinating their behavior with the fishermen,” says marine biologist Mauricio Cantor of Oregon State University.
Using drones and underwater photography, we can monitor their behavior. Fishermen and dolphins in unprecedented detail, finding that they catch more fish by working together in sync.
It is very difficult to calculate the amount of fish a mammal swallows compared to how much a fisherman catches. How does hunting dolphins with humans differ from hunting dolphins without humans?
The researchers used some clues above and below the water to find out. From above, the researchers observed the dolphins getting very close to the fishermen while giving them a signal to cast their nets - a deep dive.
Meanwhile, underwater, dolphins increase their echolocation clicks when fishermen cast their nets. When the nets fall, the dolphins also dive for a longer time. The researchers suspect that dolphins take advantage of the way nets disrupt a swarm and send individuals out on their own, making it easier for them to get stuck. Underwater footage also shows individual dolphins catching fish straight from the nets, and local fishermen report that this happens frequently.
Source news: Science Alert https://ar.rt.com/uonc