A shark warning was in effect for Imperial Beach today after a group of surfers spotted a great white just off the coast.
The surfers were near the end of Beach Avenue when they saw some dolphins scatter around 9 a.m. Tuesday, said lifeguard Capt. Robert Stabenow.
About the same time, the shark's dorsal fin appeared. One of the group used his cell phone to capture an image of the fish, believed to be 16-18 feet, Stabenow said.
Later Tuesday, an Imperial Beach lifeguard saw the image online and alerted his colleagues, who tracked down the photographer and interviewed him. Eventually, the digital image helped someone with the nonprofit group Shark Research Committee identify the shark as a great white.
Stabenow said great white sightings in the area are "very rare.''
The city then posted signs warning about the shark.
"We've got a confirmed sighting,'' he said. "It was credible. ... And we hope most of the community heeds the warning and stays out of the ocean for the next few days.''
Stabenow said the number of surfers this morning appeared down slightly, though dozens were bobbing on their boards in the same general area.
Unless the shark is seen again, the warning will expire Friday, Stabenow said.
Great whites, which can grow up to about 20 feet, mainly subsist on sea lions and other sea mammals.
