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Dolphins are the true friends of anglers! Beloved mammals herd schools of fish into trawler crew’s nets…so they can pick up any stragglers left behind, research shows
Dolphins have long been observed helping humans catch fish. Now scientists think they know why: Dolphins themselves catch more fish while keeping themselves safe.
The researchers studied drone images, sonar and acoustic recordings of the murky waters off Laguna, Brazil, where dolphins drive large schools toward waiting fishermen.
Dolphins dive as a signal to fishermen when to cast their nets, then help each other catch fish which as a result become separated from the main shoal.
Dr. Mauricio Cantor of Oregon State University, who led the study, published in the Proceedings of the National Academy of Sciences, said: “Dolphins and people have the same goal: to fish.” They can do it alone, but they have learned that they do it better as a team.’
Dolphins have long been observed helping humans catch fish by diving as a signal to cast their nets.
Anglers were 17 times more likely to catch fish, while cooperative dolphins were 13 percent less likely to die.
Cooperative dolphins off the coast of Brazil signal to fishermen, who cannot see the fish beneath the murky water, when they have left a large catch.
They do this by suddenly diving underwater, at which point the fishermen immediately cast their nets.
The researchers, who looked at more than 2,000 interactions, found that the tactic worked well, with dolphins diving and fishermen responding promptly in time about half of the time.
The clear evidence that the dolphins were benefiting came from sonar evidence that they were stealing fish from the nets.
The researchers studied drone images, sonar and acoustic recordings of the murky waters off Laguna, Brazil, where dolphins drive large schools toward waiting fishermen. [File image]
Nearly two-thirds of the fishermen interviewed said they had sensed the creatures taking some of their catch.
After herding the fish, which were mainly mullets, and having the fishermen cast their nets in response, the dolphins spent more time producing rapid clicks, so close together that they sounded like a buzz.
Unlike normal clicks, for navigation, these quick clicks indicate that the creatures are getting closer to the prey.
The dolphins also spend more time underwater after working with the fishermen.
Both behaviors suggest that the creatures were getting more fish than usual by working with the fishermen.
Anglers certainly benefited, being 17 times more likely to catch fish and catching nearly four times as many mullets when partnering with dolphins.
When the dolphins worked with the fishermen, they were 13 percent less likely to die than uncooperative dolphins.
That’s likely because the cooperative creatures tend to stay in a smaller area, so they’re less likely to end up as ‘bycatch’ in the nets of other illegal fishermen.
Dolphins have also been found to work with fishermen in countries like Myanmar and India.
However, the researchers warn that the fascinating behavior could be lost within 40 to 60 years.
This is because the number of fish is declining and the pressure on traditional fishermen could cause many to give up, losing decades of knowledge on how to work with dolphins.
The 15-year study is published in the Proceedings of the National Academy of Sciences.