Your Good News of the Day: Coho salmon population surges in Marin County creeks.

The winter rains have caused the biggest surge of coho salmon in a dozen years in the celebrated spawning grounds of western Marin County, one of California’s last great strongholds for the embattled pink fish.

At least 648 coho this winter made their way against the current up meandering, forested Lagunitas Creek and its many tributaries on the northwestern side of Mount Tamalpais, according to a new census by biologists.

The coho run is the largest in the North Bay since the winter of 2006-07 and well above the long-term average of about 500 fish. It’s the sixth-largest run since systematic surveys began in 1996.

The surge of salmon is being credited to habitat restoration efforts for the endangered fish.

The Lagunitas Creek migration is the largest run of wild coho between Humboldt and Monterey counties — most other river systems contain hatchery-raised fish — and one of the most remarkable. The fish swim 33 miles from the ocean into Tomales Bay and through the redwood- and oak-studded San Geronimo Valley, where half their spawning grounds are in developed areas, including the towns of Forest Knolls, Lagunitas, San Geronimo and Woodacre.