Ocean Geo - News and Blog
The White Shark Café
This is a post from Scuba Diver Life, by guest writer Christina Albright-Mundy
Cheers had a bar, Friends had Central Perk — having a place to decompress and meet new friends is a must for many people. And while the adoption of a local hotspot might seem a human predilection, it seems we have this in common with great white sharks: They frequent the White Shark Café.
Between the Big Island of Hawaii and the Baja Peninsula, roughly 1,200 miles from the California coastline, a mid-ocean locale draws more than half the population of California great white sharks every spring. What these sharks do once they arrive at the Café is a matter of speculation. Fish populations in this region are low, so it’s unlikely they’ve come for the tuna rolls. The sharks may be congregating to hunt giant squid, a hypothesis that was given credence by the sighting of sperm whales — known predators of giant squid — in the area. Sharks in the area, imbedded with pop-up archival transmitting (PAT) tags, also perform repetitive deep dives, adding more evidence to the theory. Giant squid are typically found between 1,000 and 2,000 feet; one shark alone clocked 96 dives with a maximum depth of 1,800 feet. It is of note, that primarily male sharks are completing these repetitive dives, not female sharks.
Another school of thought holds that this is a great white shark breeding ground. No great whites have ever been observed mating or giving birth, though scientists think breeding occurs between spring and summer. This time of year, the majority of tagged female California great white sharks are at the Café, as are all tagged male California great white sharks. By August, young great whites are caught as by-catch in Southern California, supporting the purported 18-month gestation period of these animals and the suspected dates of conception.
The exclusivity of the Café to California great whites also gives credence to its function as a breeding ground. California great whites, like most other distinctive great white shark groups, appear to only breed amongst themselves. The tracking of PAT-tagged male California great white sharks shows that their migratory patterns do not cross paths with other great white groups. From the time when the California sharks branched off from the Southwest Pacific sharks, almost 200,000 years ago, they have maintained a close-knit group. Recent mitochondrial DNA specimens have revealed that the California great white sharks and the Southwest Pacific sharks are remarkably different genetically, indicating that they have not been interbreeding for some time.
The White Shark Café as a breeding ground seems to be the most likely explanation, but it leaves us with some unanswered questions. Juvenile, sexually immature animals also travel to this locale — why? Why are the male sharks making these repetitive dives? Is it part of the mating ritual? The data may be limited and the population may be small, but thanks to scientific advancements, we can at least say with certainty where these sharks will be heading in a few months.
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