Men and fishing for dolphin have been related since time immemorial. Pliny the Elder (23-79 AD) already mentions, in his natural history, interactions in fishing. There are records that span different times and continents, examples ranging from the Mediterranean to North Africa and Australia. However, there is a unique case, a type of cooperative fishing between men and dolphins, in the state of Santa Catarina, in southern Brazil, where it is these cetaceans who direct and control the work.
Carlos is 50 years old and his skin is tanned by the sun. He belongs to a family with three generations of fishermen: grandparents, children, and grandchildren. He has just arrived, with his bicycle, at the beach of Mar Grosso; more precisely the Molhes da Barra, a long breakwater built artificially in the 1970s. This separates, on the one hand, the open sea and, on the other, an extensive channel that connects a system of three lagoons, brackish and interconnected, with the Atlantic Ocean. Carlos lives in the city of Laguna, located at the entrance of the San Antonio lagoon (the other two are Imari and Mirim).
It is very early and the sun has not yet illuminated the beaches. Other fishermen also arrive, some walking and others by bicycle. They arrange their nets while watching the water eagerly, looking for their fishing partners, who will come from the open sea and swim in the channels: they are bottlenose, bottlenose, or toning dolphins ( Tursiops truncatus ). Surprisingly, the men won’t touch the water until their homework partners show up.
Fishing For Dolphin Begins
With the arrival of the dolphins, the human fishermen take their positions: they stand next to each other, with the water almost waist-deep, forming a single row, parallel to the shoreline. In his bare hands, the fishing net ( Zarafa, in Portuguese) is a circular nylon mesh, with small weights on its edge and in the center a long rope that holds it attached to the fisherman.
The water is extremely cloudy, has less than a meter of visibility and the men cannot locate the fish. But the other actor in this scene, the dolphin, does not need to see the shoals since it has an echolocation system, a very precise biosonar that through the emission of short duration and high-frequency sounds – between 250 and 220,000 hertz – and its subsequent reception after hitting an object, forms a three-dimensional ultrasound image in the emitter. This allows you to identify the direction of the school, its distance, its speed of movement, the number of fish that make it up, and even the species to which they belong. One thing to keep in mind is that the human ear perceives sound waves between 20 and 20,000 hertz,
Men wait. One or two dolphins swim slowly, coming out periodically to breathe. Only the blowhole — single breathing hole — and occasionally part of the head and mouth are seen. Their breathing is clearly heard, like a rapid, loud breath.
Suddenly a dolphin dives away from the fishermen, turns in fast circles, now only its dorsal fin is visible; in seconds, his movement changes, he heads towards the men in a line on the coast and signals. The fishermen in front of him cast their nets and catch the fish, which become entangled in the nets. Finally, they drag the nets to the beach and the other fishermen who have been waiting for their turn take their place in line.
Now Fishing for Dolphin
What is the dolphin sign? It swims toward the fishermen, stops abruptly, and begins a quick swim — about five or seven meters from the human line. This distance keeps you safe, out of reach of the nets. It then fully pulls its head, back, and dorsal fin out, arching in a rapid and exaggerated way in a half jump, very different from surfacing for breath. This happens in Laguna. In Tramandai – some 250 kilometers further south – dolphins also collaborate with humans in fishing, but the execution of the signal is very different. There the dolphins approach the line of fishermen, stick their head out of the water, looking at them, and repeatedly move it back and forth. No dolphin makes the signal without first exhibiting the full sequence of behavior: diving, get away from the fishermen, and return to them in a straight line. In addition, the signal not only indicates the presence of the fish but also the direction of their movement, the vigor of the same, and the size of the school. The fishermen immediately interpret the message of the dolphin, they are true experts in the behavior of these animals.
Fishing For Dolphin in numbers
Cooperative fishing has been going on since 1847 and at least three generations of humans and dolphins have participated in it. This is the case of Chinelle, a female dolphin who had two descendants; the daughter, in turn, already has a baby. All of them have been actively involved in fishing. This is done daily, ten months a year, even in bad weather. In the fishing session we witnessed, sun and rain alternated; the fishermen did not get out of the water until they completed their work.
The main preys are the modules or mullets ( Mugil cephalus ), which in Portuguese are called train has. It is not by chance that in Laguna this species constitutes 92% of the fishing product, and that the highest catches occur between April and June since this is when the mullets are migrating. Juvenile fish, on the other hand, are caught mainly between November and March. Only in the months of July and August — winter in the Southern Hemisphere — does the activity cease. Captures of other species, such as Micropogonias furniture, have been reported in September and October. This method of fishing is very efficient for humans. Fishing with botos, as they call dolphins in Portuguese, they catch more fish, larger and heavier – 30 to 50 centimeters long and two kilos in weight – than if they did it the traditional way. Most of the product of the catches is sold in the markets of the city of Laguna, which supports about 100 families.
But it still needs to be detailed how dolphins benefit. They take advantage of the confusion caused by the net falling on the shoal. The fish that escape from the net cannot flee towards the beach, because there is the wall formed by the legs of the fishermen, and when they enter the sea they find the toothed mouths of the cetaceans. Successful fishing by humans is generally accompanied by mullet caught between the jaws of dolphins.
The Russian researcher Vsevelod Bel “Kovich has reported dolphins fishing for mullet in the Black Sea, for which they must develop a variety of cooperative strategies since the search times for prey are long and individual pursuits are not very productive. The fishing method in Laguna is easy and successful, even for mothers with young, catching fish with minimal effort.
It is important to note that the fishermen do not call or signal the dolphins, they in no way affect their behavior. Furthermore, they never give them fish or try to touch them. Both men and dolphins work, without distractions.
On one occasion a dolphin got caught under a net and pulled it; It is not difficult to imagine the strength of this animal, almost three meters and more than 300 kilos. As we already mentioned, fishermen have one end of the net tied to their hand; the dolphin dragged the fisherman, who was left with a dislocated arm. However, no one blamed the dolphin; after all, it was a work accident for everyone.
Also, you can read more about this article: How Long Can Fish Go Without Eating
Cultural transmission between dolphins?
The term “cultural transmission” is used in ethology — a discipline that studies the behavior of animals in their environment — to define the process of learning by imitation in animals (see box). Until recently the most prominent examples came from certain primates and songbirds, but it has already begun to be considered that dolphins could also be included. These animals, which are widely distributed and live long present great social complexity. In particular, dolphins that fish in collaboration with humans in southern Brazil exhibit highly ritualized, repetitive, and highly coordinated human behaviors. Several studies have made it possible to detect elements that support the idea of a cultural transmission of these behaviors, that is,
1) They occur in certain regional communities and do not appear in others, where the environmental conditions are approximately the same: they occur only in Laguna and Tramandai and not in other beaches in the region.
2) It is passed between generations. In the case of Laguna, at least three generations are known.
3) Much of these regional communities remain in place. Dolphins can be identified through photos of their marks and scars on the dorsal fin and back. Thus, resident individuals have been identified, at different times and over the years, both in Laguna and in Tramandai.
4) A large part of the dolphin population disseminates this behavior: 40% of the dolphins in Laguna and 100% in Tramandai develop cooperative fishing behavior.
5) It is transmitted between mothers and children through social facilities and imitation. This is reinforced since the young remain with their mother for around three years.
6) There is evidence of what could be direct instruction. Mothers with young have been seen in Tramandai. approaches to fishermen with their nets; sometimes the mothers went alone while the calf stayed away, and sometimes they fished together.
7) There are differences in behavior between regional communities. In Laguna the signal is the vigorous semi-jump; in Tramandai, the movement of the head.
It is interesting to note that not all Laguna dolphins participate in cooperative fishing. Some of them even steal the fish, spinning in the water and lifting nets loaded with mullets. Fishermen call these dolphins bad — in Portuguese, ruim — to differentiate them from the good ones, who work with them.
Cultural transmission in animals
Behavior is a complex interaction between certain pre programmed patterns in individuals and the effect of the environment through learning.
Learning allows behavior to be finely adjusted based on experience and is a characteristic of many animals throughout the biological scale. The essential capacities and forms of learning are similar in many animals, but the more complex the nervous system in question, the more complicated the patterns of association and memory are. These patterns are also more complex in organisms that have a longer life span. For example, learning in many insects (with their notable exceptions) is more limited than in birds or mammals. There are several ways to learn, but the most common has to do with individual experience (through trial and error) or with learning from the behavior of other individuals. The latter is called “copied” or “imitation”. For example, in humans, language is a complex pattern of behavior that we learn from other individuals (in addition to the congenital tendency to learn it) and that is shared between generations. Because the essence of this learning is very similar to imitation (or is imitation), ethologists have called it “cultural transmission.” More formally, ethologists have defined cultural transmission as the “process of social learning within and across generations.” Based on this definition, it is easy to identify behavioral patterns of many animals in this category. Examples are abundant: there are songbirds learning local dialects; some populations of ravens break seeds by throwing them into the avenues; certain birds open milk bottles in cities; some Japanese monkeys developed the behavior of washing a type of sweet potato before ingesting it. In summary, according to the above definition, the learning process by imitation or cultural transmission is similar in animals and in human societies, and therefore it is not surprising that animals develop behaviors that are useful to them and that other animals in the community learn them. Furthermore, this is another evidence of the continuity of our origin (although this hurts some susceptibilities). and so it is not surprising that animals develop behaviors that are useful to them and that other animals in the community learn them. Furthermore, this is another evidence of the continuity of our origin (although this hurts some susceptibilities). and so it is not surprising that animals develop behaviors that are useful to them and that other animals in the community learn them. Furthermore, this is another evidence of the continuity of our origin (although this hurts some susceptibilities).
What possibly has a different connotation is culture (and not its transmission), although it all depends on which definition is used. In animals a series of classic examples of cultural transmission are known, however, we are still far from understanding if this transmission is volitional, that is, if there is the purpose of teaching in animals, which is an attribute of human culture. There are examples of chimpanzees and perhaps elephants that seem to teach behavioral patterns to their young; however, it is very difficult to demonstrate a willingness to teach without first resorting to simpler explanations.
Jose Luis Osorno
Hilda Suárez and Alejandro Balbiano are biologists who graduated from the University of Buenos Aires, Argentina. Hilda is a professor of natural sciences and education coordinator at the Instituto de Conservación de Ballenas, an Argentine affiliate of the Whale Conservation Institute. Alejandro has been dedicated to photography since 1984, a profession in which he has won several awards and also collaborates with the Institute.
We are grateful for the advice of Dr. José Luis Osorno, a researcher in ethology in the Evolutionary Ecology Department of the UNAM Institute of Ecology.