Dolphins and fishermen both benefit from collaborating to catch fish. This is shown by a new study with Swiss participation after a 15-year investigation of this practice on the southern Brazilian coast. However, this fishing tradition is endangered.
Dolphins drive schools of fish towards the coast off the Brazilian city of Laguna, increasing the availability of prey within reach of fishermen, the researchers wrote in the study published Monday in the journal Pnas. They have now been able to prove that the dolphins actively control this behavior.
Fishermen watch dolphins
« We knew that the fishermen observed the behavior of the dolphins to determine when to cast their nets, » study leader Mauricio Cantor said in a statement from Oregon State University. « But we didn’t know if the dolphins were actively coordinating their behavior with the fishermen. »
The researchers found that the dolphins benefit from a 13 percent higher survival rate compared to their lonely hunting counterparts. The fishermen, in turn, catch around four times more fish than without the marine mammals.
The researchers emphasized that the cooperative behavior of the dolphins is not genetically determined. Rather, it is a peculiarity of the dolphin population at Laguna. Both dolphins and humans would pass on their knowledge to subsequent generations.
However, model calculations show that the cooperation between dolphins and humans is at risk. The number of fish in the region has declined sharply in recent years. The coastal population is also less interested in learning the special hunting technique.
For the study, researchers observed the behavior of fishermen and dolphins for around 15 years. They also used drones and underwater photography. A researcher from the University of Zurich was also involved in the study.