Every winter and spring, great white sharks swimming off the coast of California gather in a remote area as large as the state of Colorado, for reasons scientists are still unsure of.
White Shark Café is the name of a mysterious meeting place for white sharks (Carcharodon carcharias) is located in the Pacific Ocean, between Baja California and Hawaii. The sharks make a month-long journey from their usual habitat off the coast of California to reach Café. The area has long been thought to be an ocean “desert” with little life, raising questions about its role in the lives of great white sharks.
Barbara Block, a professor of marine sciences at Stanford University’s Hopkins Marine Station, came up with the name “White Shark Café” while studying the migration patterns of North Pacific white sharks using electronic tags. Between 1999 and 2000, Block and her colleagues tagged six sharks off the coast of California and tracked their movements for six months.
Four sharks swam southwest toward Hawaii and stayed in remote waters as large as Colorado throughout the winter and spring, revealing for the first time that North Pacific great whites spend extended periods at sea. The data also showed that the sharks dived as deep as 450 meters below the surface at this location, puzzling scientists.
In the years since, the team has found that these were not just a group of adventurous white sharks migrating offshore, but that they were in large numbers, further adding to the mystery. California’s coastal waters provide great white sharks with a rich food source of elephant seals and other marine mammals, so scientists have been puzzled as to why the sharks would travel to such a remote location in the middle of the Pacific Ocean.
In 2018, a team led by Block tracked great whites to their gathering places to better understand why they chose the Café. They fitted 20 sharks with satellite tags that were programmed to fall off after a set period of time, and collected 10 tags that contained information about the sharks’ movements and diving behavior. They also collected information about the Café’s environmental conditions and marine life.
Rather than resembling an underwater desert, the team found that it was an ocean oasis. Thick layers of microalgae and a rich marine fauna suggest that the Café is much more vibrant and fertile than scientists had thought, suggesting that great white sharks congregate there each year for food. Why the sharks actively seek out this food source rather than staying in their usual habitat is unclear.
“We found a high diversity of deep-sea fish and squid (over 100 species), which combined with remotely operated vehicle (ROV) observations and DNA sequencing, demonstrates that this is a viable food source to support large pelagic fish such as sharks and tuna,” Block said.
The sharks’ diving patterns mirrored the daily cycles of animals that migrate up and down the water column, suggesting the sharks were following their food. But the diving also raised questions about mating behavior, which the team was trying to understand.
Male sharks increased their diving activity in April, up to 140 dives a day, but the habits of the females did not change. Researchers are still wondering what this means, but some experts think the males may dive deeper to increase their chances of mating.