Industrialized maritime transport represents a “significant threat” to the whale shark, and may be causing a significant number of deaths worldwide, concludes a study in which researchers from the University of Porto participated.
In a statement, the Center for Research in Biodiversity and Genetic Resources (CIBIO-InBIO) of the University of Porto clarifies that the study, published in the scientific journal PNAS, indicates that “deadly collisions between whale sharks and ships are largely underestimated”. .
“Since this species spends a lot of time on the surface and usually forms coastal aggregations, it is thought that collisions with ships could be causing a substantial number of deaths. However, there was no way to monitor this threat in the past”, stresses the center.
Whale sharks can grow up to 20 meters in length and feed on zooplankton (a set of aquatic organisms), helping to regulate their levels in the ocean.
According to the research, coordinated by scientists from 50 international institutions, these collisions may “even be the main reason” why whale shark populations “are in decline”.
Over the course of the study, researchers tracked the movements of 350 whale sharks (through the Global Shark Movement) and ships around the world by satellite, identifying areas where the risk of collision is high.
After mapping the overlap between shark ‘hotspots’ and the global fleets of cargo, oil, passenger and fishing vessels, the researchers concluded that “more than 90% of the areas occupied by sharks overlapped with ships”.
“The study also showed that many satellite transmitters stopped working on the busiest shipping routes, even after discarding transmitters with technical failures”, notes CIBIO-InBIO, noting that the team concluded that the failure in transmissions was possibly caused by a collision, this is because “sharks sink after they die”.
Cited in the statement, Freya Womersley, a researcher at the University of Southampton and leader of the study, says that industrialized shipping “may be causing the decline of whale sharks”, a species “extremely important in the oceans”.
“We need to invest more time and energy in developing strategies to protect this endangered species from commercial maritime transport before it’s too late”, appeals the PhD student.
Also David Sims, a researcher at the University of Southampton and co-founder of the Global Shark Movement project, notes that some of the satellite transmitters showed whale sharks that were on busy routes “slowly sinking to the bottom of the sea, most likely due to a collision with a ship”.
Researcher Nuno Queiroz, from CIBIO-InBIO, highlights that there are no “global measures” to protect the species against collisions with large ships.
The researchers hope that the study can motivate the creation of management measures to protect the populations of whale sharks, a species that “faces an uncertain future”.