Warming will make tiger sharks more vulnerable, and changes in their migration patterns could not only disrupt local ecosystems, but also increase the number of shark encounters with humans.
Due to global warming, the climate zone is shifting, which means that flora and fauna migrate to new habitats or change their habits. In many cases, this is due to the fact that spring began to come a few weeks earlier than in the past.
The authors of the new work studied how these changes affected tiger sharks: over the past 40 years, the range of these heat-loving predators has expanded significantly throughout the North Atlantic. This means that the paths of their annual migrations are getting closer to the pole and extend beyond the boundaries of protected areas, so predators can become victims of fishing. In addition, changes in their migration disrupt natural ecosystems and increase the risk of human encounters.
Migration routes of tiger sharks have shifted poleward in recent years, due to rising ocean temperatures. As a result, tiger sharks have moved to that part of the Atlantic, which is not protected by law. This makes them vulnerable to poachers and fishing boats.
Neil Hammerschlag, study authors and assistant professor at the University of Miami
The researchers found that the changes affected the Atlantic populations of tiger sharks (Galeocerdo cuvier) – this is one of the largest and most active predators in the oceans. These sharks prefer to live in warm water, so they regularly migrate south and north during winter and summer.
Scientists have collected all the early data on tiger sharks and combined them with newer data collected over a decade of satellite observations. Sensors attached to the sharks’ dorsal fins have made it possible to track the movements of predators without the need for recapture.
As a result, it turned out that Galeocerdo cuvier reacted very strongly to any changes in the average water temperatures. An increase of even 1°C caused the sharks to swim 400 km further towards the north pole, and the migration started two weeks earlier than usual during the spring.