Wild coho salmon returned to Lagunitas Creek in west Marin County last week following a period of gentle rain, activists with the Salmon Protection And Watershed Network said.

The endangered fish revisit their natal streams when the rains begin in the fall and may be spotted spawning from November to January.

Bright red and 24 inches long, coho salmon come to the creek from the ocean to lay their eggs before dying. The dead become fertilizer for Redwood trees along the creek.

“It’s an incredible spectacle to watch these fish leap waterfalls, hear them splash around as they maneuver up shallow riffles, and witness the hooked-nose males fight for the opportunity to fertilize the female’s eggs in the nest she builds and protects until death,” said Ayano Hayes, watershed biologist for SPAWN.

Hayes said, “This is the part of their epic journey of coming home, as these fish left their natal streams a year and half ago for the ocean as cigar-sized fish. The ones that have survived their ocean phase are now migrating back as two-foot adults after only 18 months at sea.”

“It’s an incredible spectacle to watch these fish leap waterfalls, hear them splash around as they maneuver up shallow riffles, and witness the hooked-nose males fight for the opportunity to fertilize the female’s eggs in the nest she builds and protects until death.”

Ayano Hayes, watershed biologist for SPAWN

Coho salmon have been on the decline in Lagunitas Creek. Only about 500 return each year to spawn, compared to 5,000 five decades ago. It is illegal to fish coho salmon in California.

Nonprofits and government agencies are spending money to try to revive the population in Marin County and Central California.

“Coho salmon are iconic keystone species that are critically important to protecting Redwood ecosystems, by bringing nutrients back from the sea to feed the trees and wildlife of our region that help sequester carbon and help moderate climate change,” said Todd Steiner, ecologist and executive director of Turtle Island Restoration Network, which oversees the Salmon Protection And Watershed Network.

Turtle Island Restoration Network leads public nature tours to view the fish without disturbing them. Their website also suggests viewing locations where people can go to see the spawning fish.