Kayakers, boaters and surfers should avoid a group of gray whales swimming less than a mile off the Pacifica coast, marine officials have warned. 

Three adult whales and two calves found the thriving feeding spot about a month ago. When word got out that the giant sea mammals were nearby, interested observers started paddling out to see them. 

Officials are now concerned that the spooked whales will abandon the calves or leave the feeding ground. 

The Marine Mammal Protection Act states that humans must stay at least 300 feet from protected species like gray whales or face civil and criminal charges. 

“We are taking this opportunity to educate the public about the gray whales, their migration patterns and why they are here,” said Amy Gubser, a youth surf instructor at Surf Camp Pacifica. 

Observers can safely watch the whales from a distance with binoculars or a spotting scope, said Mary Jane Shramm, a spokeswoman for the Gulf of the Farallones National Marine Sanctuary. “They are fantastic, but we need to let them be.” 

Typically, gray whales feed on microscopic crustaceans in the Arctic seas. But global climate change has caused the numbers of those critters to plummet, forcing whales to seek out other feeding grounds. 

Researchers don’t know what the whales have found so tasty in Pacifica. Tests are planned to see if the food may be contaminated because of nearby sewage outfalls, Shramm said in an e-mail. 

Federal regulatory agencies including the National Oceanic and Atmospheric Administration Office of Law Enforcement have been notified about the situation, she said. 

By Justin Wiley, Chronicle Staff Writer 

San Francisco Chronicle June 13, 2009