On a July morning in 2013, a great white shark named Lydia was swimming across the North Atlantic Ocean. As the sun rose over the waves, she made an abrupt descent into the abyss. She dove down, deeper and deeper, until she reached her destination a kilometer beneath the surface. Lydia swam to the very bottom of the mesopelagic, a cold, twilight realm where little light penetrates, yet life still teems. One estimate suggests as much as 95 percent of the world’s fish live in the mesopelagic. Their swarming masses are punctuated by larger animals such as cephalopods and, apparently, great white sharks.
While the depth of Lydia’s dive was impressive, it was the means by which she got there that has added fresh insights into our understanding of shark ecology, and how migratory predators survive in the relative desert of the open ocean.
With location, temperature, and depth sensors surgically attached onto Lydia’s dorsal fin, a team of scientists led out of the Woods Hole Oceanographic Institution (WHOI) followed the 900-kilogram, 4.5-meter-long shark for six months, recording when and where she surfaced and garnering information about each dive when she disappeared.
Photo: Elias Levy/Wikimedia Commons