For two years a team of researchers has been busy with the great white shark count. They worked in the Farallon Islands off Central California, one of the few known homes to great whites.
Barbara Block is a Stanford University professor who says years of study and photographs help unlock the population mystery. It turns out the dorsal fin acts like a fingerprint.
"Photographs showed us that we could, with marks right on the fin, identify individuals and we've actually seen a shark called TJ over five times for 22 years of records," said Block.
The marine biologists took more than 300 pictures and made more than 130 unique matches. The findings have just been released in the journal Biology Letters.
Researchers say they relied on sophisticated mathematical models to determine how many great white sharks live off Northern California's coastline. That number is 219.
In addition to that precise figure the team came up with a population range from a low of 130 to a high of 275. Dr. Chris Harrold of the Monterey Bay Aquarium warns this first-ever count should not automatically trigger alarm.
"It's only a number and we don't know whether that number is going up or down," said Harrold. "We don't know whether that number is somehow too big or too little. It's just a number."
The low number in itself, however, does indicate there is not a lot of room for error when it comes to white sharks.
"We have to remember that they are threatened, that these animals do interact with human fishing gear and that they need in all forms of their life history to be protected," said Block.
Since the great white has no predators except man, there is a logical source for credit or blame if the number changes.