If you’ve ever witnessed a shark breach the water—whether in person or somewhere on the Internet—that fleeting but awe-inspiring moment is just a small fraction of the time it spends at the surface of the ocean. Most of the time sharks and other large marine predators are out of sight, begging the question—where do they go?
A new study demonstrates that large predatory fishes like sharks, tunas and billfish make a surprising number of visits to the deep ocean—particularly the mesopelagic zone, which is found between 200 to 1,000 meters below the surface. This area, also called the ocean’s twilight zone, has been overlooked as critical habitat for large predator species, according to the study. The paper is published in the journal Proceedings of the National Academy of Sciences.
Led by Camrin Braun, an assistant scientist at the Woods Hole Oceanographic Institution (WHOI), the study incorporated an astonishing amount of data from multiple scientific partners. He and the co-authors synthesized data from electronic tags, shipboard sonar, Earth-observing satellites, and data-assimilating ocean models to quantify the ecological significance of deep diving for large pelagic predators. They emphasize that a healthy mesopelagic zone provides numerous benefits and ecosystem services to humans as well.
“No matter what top predator you look at, or where you look at them in the global ocean, they all spend time in the deep ocean,” Braun said. “All of these animals that we think of as being residents of the surface ocean, use the deep ocean way more than we previously thought.”
The scientists leveraged data from 344 electronic tags over the course of 46,659 tracking days for 12 species in the North Atlantic Ocean, including white sharks, tiger sharks, whale sharks, Yellowfin tuna, swordfish and more.
2023-11-07 11:41:04
Original from phys.org