The dreaded sharks, known for being the ocean's deadliest hunters and taking moviegoers to the movies to see director Steven Spielberg's films, are now getting obese. The phenomenon was observed in animals that live near the beaches of Miami, in the United States.
Recently, a study published by the journal Science of the Total Environment in partnership with the Fapesp agency (Fundação de Amparo à Pesquisa do Estado de São Paulo), revealed that the nurse shark ( Ginglymostoma cirratum ) has been accumulating fat in the body. One of the reasons is that she lives close to urban areas.
Professor and biologist Leonardo Marconato da Estácio explains that “sharks are more sedentary, as they have a gill ventilation system even when they are immobile. Other species, when they stop swimming, die.”
“The presence of fatty acids from bacteria, common in sewage, was identified in the waters of Miami where these sharks live. In addition, there are other indicators, such as the construction of ports and the activities of fishermen in the region, who throw fishing scraps, which makes it easier to obtain food”, highlights professor Rubens Oda, from Faculdade Descomplica.
With a flat body shape, the nurse shark gets its name because its skin has a very rough texture, similar to sandpaper. In addition to its appearance, the animal has a mustache that allows it to find food at the bottom of the sea.
The journal Science of the Total Environment also highlighted that other species — such as the blacktip shark ( Carcharhinus limbatus ) — are not affected in the same way as nurse sharks. The reason? Professor Antônio Mataresio Antonucci, from the Veterinary Medicine course at Faculdade Anhanguera, in Sorocaba, emphasizes that the difference is due to the characteristics of each species.
“Unlike the nurse shark, which is more sedentary, which lives close to urban areas and does not move as much, using less energy, the blacktip shark inhabits an area further away from the coast and is willing to swim more, being more active. .”
Can fat accumulation shorten nurse sharks' lives?
“We can't say, because there aren't enough studies to prove that the accumulation of fat affects the lifespan of these animals”, says Antonucci. “But, based on mammals – which, if they eat too much, end up gaining weight and decreasing their life — we might consider nurse sharks to be more at risk, but that's not a certainty.”
For biologist Leonardo Marconato, there is no precision about the longevity of animals, especially when evaluating the effects of urbanization and pollution. “There are no studies in this regard to claim that there is a decrease in life span.”
What can be done to preserve the lives of sharks?
Pollution and uncontrolled exploitation of natural resources put marine life at risk. “When we think about this kind of impact, we can't help but think about the wrong of sustainability: reduce, recycle, reuse, rethink and refuse”, says Professor Rubens Oda. “Sewage must be treated before it is dumped into the sea.”
* Intern at R7 under the supervision of Karla Dunder