CALIFORNIA BRIEFING / MARINA DEL REY

A 20-foot gray whale that had been frolicking in the Marina del Rey channel for about three weeks left the area recently and appeared to be heading north to Alaskan waters, according to rescuers.

The whale was last seen Friday, swimming north from Marina del Rey past the Santa Monica Pier, and along the coast about 400 yards offshore before heading for deeper waters, said Peter Wallerstein, founder of Marine Animal Rescue in Los Angeles, who tracked the whale with binoculars.

The mammal probably stopped in Marina del Rey on its way to Alaska from Baja California, Wallerstein said.

It stayed there for weeks, roaming around, going out to sea and then returning, he said.

Wallerstein said that about 6:30 p.m. Friday, “something clicked in the whale,” indicating that “it’s time to go.”

California gray whales migrate south each winter to the waters near Baja California, then return to Alaska in late winter and early spring.

“I felt relieved. It got to be a real problem with boats getting too close, and I was worried about the safety of the whale,” Wallerstein said.

-- Ari Bloomekatz