One of the last runs of wild coho salmon in California has surged into the Lagunitas Creek watershed in western Marin County , bringing renewed hope to fisheries experts, watershed managers and those who have devoted their lives to salmon procreation.

The endangered fish had all but disappeared over the past two years, creating fear among biologists that the species was in the midst of a death spiral. Then, during rains this past week, the fish arrived and began laying eggs in the creek and tributaries, which wind through the lush San Geronimo Valley.

Biologists with the Salmon Protection and Watershed Network, or SPAWN, the Marin Municipal Water District and the National Park Service counted 55 coho and 30 egg nests, or redds, in Lagunitas and San Geronimo creeks and in Devil's Gulch over the past week.

"That's the most that we've seen in a single week in three years," said Eric Ettlinger, the aquatic ecologist for the water district. "After two terrible years for coho, it's a relief to have more fish returning to Lagunitas Creek, so I'm cautiously optimistic that we've seen the worst of the population decline."

Largest wild run

The Lagunitas watershed, which winds 33 miles through the picturesque redwood- and oak-studded valley on the northwest side of Mount Tamalpais, supports the largest wild run of coho salmon along the Central Coast and is considered a model for fisheries restoration around the state.

It is unique in that the primary spawning grounds are in the middle of developed communities. Some 40 percent of the coho in the watershed are hatched in tributaries surrounded by homes, golf courses, roads and horse corrals in the 9-square-mile San Geronimo Valley

Coho in Central California were listed as endangered in 2005 under the Endangered Species Act. The Lagunitas is considered by fisheries biologists to be the last true refuge for wild coho on the Central Coast. There are bigger runs elsewhere - especially after the dramatic decline over the past two years - but many of the coho in other places were raised in hatcheries.

Run still below average

Marin's wild coho took their time this year - they usually swim up the creek during the first rains - and even though their undulating figures can be seen over the gravel beds, the numbers are well below average for this time of year.

Last winter, 67 live fish and 51 redds were spotted during spawning season. The year before that, 43 fish and 26 redds were counted. Those two years are the worst on record.

In 2004-05, 1,342 coho were seen in the watershed. Those fish left 496 egg nests. The average since 1995 is 524 fish and 217 redds in Lagunitas Creek and its tributaries.

While the fish now in the creek are encouraging to water and fisheries managers, not everyone is so optimistic.

"We are down to the end of the line," Todd Steiner, the executive director of SPAWN, said. "Despite better than average rainfall and early rainfall, which is normally good for coho, we didn't see fish until about two weeks ago. The National Marine Fishery Service is saying we're in an extinction vortex. We're at the now-or-never point."