Throughout the year, more than 40 species of sharks swim near Portugal. However, not all of them are easy to see: most never come close to the beach and some remain only in the depths.
There are many reasons that bring sharks to the Portuguese coast.“The blue shark, for example, is found along the entire Portuguese coast — in fact, almost from the Bay of Biscay to Morocco. The Atlantic Ocean is a nursery for females to give birth, this species is born here, so it is relatively easy to see”, explains Nuno Queiroz, researcher at the Research Center in Biodiversity and Genetic Resources (Cibio-inBIO) of the University of Porto. In addition to the blue shark, in Portugal you can see the mako shark, the great white shark and the basking shark, among others. In the Azores, it is common to see the whale shark.
The Portuguese coast becomes attractive for these predators, especially in summer, because of a geographical phenomenon called upwelling (outcrop, in Portuguese). This phenomenon, which consists of water rising from depths to the surface, not only makes the water colder, but also brings nutrients from the bottom that trigger a greater concentration of zooplankton, which attracts prey and predators.
“This outcrop system, which is quite common, makes these areas places where predators such as sharks congregate, because they are looking for food. Generally, the outcrop is common in summer; It’s the reason why we go to the beach and the water is cold, because it comes rich in nutrients from the depths”, says Nuno Queiroz. “Sharks are not on the coast for the temperature itself, because there are species that like warm waters and there are others that like cold waters, but for the food,” he adds.
O upwelling It exists in many parts of the world, such as Chile, Namibia, Angola and Portugal. When this phenomenon occurs, it is accompanied by a thermal front, an area where two air masses with different temperatures and densities collide.
Sharks spend a lot of time exploring thermal fronts, explains the biologist. In the Algarve, one of the places where it is easiest to see sharks, there is a front that exists throughout the year. In the past, fishermen hunting sharks would carry a thermometer on the boat to see where the temperature variations were strongest. Now, monitoring is done with satellites.
“Fishermen know that the probability of catching an animal is greater in these areas. There are fronts, like the one in the Algarve, that are persistent, but hundreds form every day along the coast”, observes Nuno Queiroz. Portugal is the world’s second largest exporter of shark meat, according to the environmental association ANP/WWF.
The scientist claims that shark sightings are becoming more and more frequent. “There seems to be an increase in sightings near the coast, which was not very normal in the past. There could be many reasons for this: the species could now be more abundant, the shark population could be moving much closer to the coast or there could also be more people seeing them. As there are more people on the beach in the summer, you end up seeing more sharks. In fact, there was a species, the basking shark, what was said in the past that hibernated in winter, because in summer they were so common and in winter no one saw them, but that is not true”, explains Nuno Queiroz.
Sharks swim in waters within specific temperatures, which vary according to each species’ preference. Therefore, the global warming and subsequent changes in ocean temperatures could determine which species of sharks swim along Portuguese coasts. Portugal will not be one of the areas most affected by this phenomenon, but it may feel some effects.
“Normally, the shark limit is marked by a temperature much colder or much warmer than what is found here [em Portugal]”, notes the researcher. “What is happening in most species is that their limit, especially the cold water limit, is moving further and further north, so there are sharks that are moving further north. There are species that have their southern limit close to here, like the basking shark; so, in the future, they could disappear from the Portuguese south coast,” he adds. The effects caused by the disappearance of a shark are not yet well known. On the other hand, In 50 or 100 years, and also because of temperature changes, sharks from more tropical waters could appear on the Portuguese coast.
“Typically, there are few unprovoked attacks”
Most of the sharks present on Portuguese coasts do not pose a danger to swimmers. These predators rarely swim beyond the surf, close to the beach. On the few occasions when they get close, “they are not worried about people at all”, says Nuno Queiroz.
The Cibio researcher states that sharks are curious animals, “but also very cautious”. The danger of an attack is almost zero. Around the world, sharks that attack swimmers exclusively to eat them are rare. In fact, in Portugal, according to Nuno Queiroz and the International Shark Attack File, There are no officially recorded unprovoked attacks.
However, it is important to take precautions. It is not recommended to be in the water when there is poor visibility, such as at night or during low light hours, times when sharks are most active. “During the day, when there is light, the shark recognizes that swimmers are not its normal prey and ends up ignoring them completely. There are areas where sharks can swim among people without them realizing that the animals are there”, says Nuno Queiroz.
The biologist also explains that, although there are species that can be more dangerous than others, “normally, there are few unprovoked attacks”. Among the species that can be seen in Portugal, the one that attacks most frequently is the nurse shark, which tends to be at the bottom of the ocean. “It’s a very slow shark, people go there and pull the animal’s tail or take photos up close and, therefore, the animal ends up feeling attacked”, explains the biologist. In case of a shark sighting, it is best to leave the water calmly, as, warns the scientist, sounds and sudden movements can make the animal “even more curious”.
Text edited by Ana Maria Henriques
