Biologists believe only 219 full-grown or near-grown adults inhabit the coastal waters between Bodega Bay and Monterey each fall. Based on populations of similar top-level predators such as killer whales and polar bears, scientists thought they would find more great whites.

Still, the shark-counters say it’s too soon to tell what the low number means.

“This estimate only represents a single point in time,” said Taylor Chapple, who led the study as a doctoral student at the University of California, Davis. “Further research will tell us if this number represents a healthy, viable population, or one critically in danger of collapse, or something in between.”

Great whites typically linger along California’s north-central coast from late summer through the end of fall to feed on a rich stock of seals, sea lions and other marine life. Come January, the sharks begin a massive migration that takes them as far as Hawaii, as demonstrated by satellite tracking of the animals in recent years.

To conduct the shark census, researchers ventured by small boats into waters known to be frequented by sharks. Using a seal-shaped decoy, they lured great whites close enough to take photos of the jagged edge of the sharks’ dorsal fins, which serve as a kind of fingerprint unique to each individual shark.

From these photos, they counted 131 individual sharks and used a statistical model to extrapolate to 219 sharks total.

The results of the study are being published this week in the journal Biology Letters.