Success for Coho salmon at BLM California's Headwaters Forest Reserve

Over the last year, salmon spawning numbers skyrocketed in the BLM-managed Headwaters Forest Reserve in California. This spawning success is an indicator of the improved health of the forest itself, which was established as a forest reserve in 1999 to protect some of the last untouched ancient redwoods on California’s North Coast.

The heavy rains of December 2022 and January 2023 drastically improved river breeding areas for salmon migration in the South Fork Elk River, a key waterway in the Reserve. Zane Ruddy, BLM California Arcata Field Office fish biologist, said evidence of this success was borne out in recent fish surveys.

“Typically, we can complete a spawner survey along the Elk River in a few hours, but this year it took two days to complete. There are fish and redds (their nests) around every river bend. We counted 140 spawners in one day, which exceeds what we normally see in a whole season,” he said.

In addition to the heavy rains, the BLM’s “wood is good” watershed restoration project has also made a difference. As part of the project, trees removed from the forest in thinning operations are placed in key areas of the Elk River, creating fish habitat.

“It’s been incredible to watch the fish use newly formed habitat,” Ruddy said. “Many areas that were previously simple and shallow now have spawning gravels and deep pools, perfect for the young salmon to live [in] before swimming to sea.”

Once salmon return from the sea to the river, they spawn, and their life cycle is complete. Even then, they contribute to the health of the redwood forest ecosystem. Salmon are primarily eaten by wildlife, who pull them out of the river, usually eating about half of each fish. These remains contain nitrogen and phosphorous from the sea, both of which enrich the surrounding forest.

By examining these salmon remains, scientists track how nitrogen from the ocean spreads through the forest. They use an isotope analysis to identify nitrogen atoms called N15. These atoms are abundant in marine algae but rare on land. When scientists find N15 in the Headwaters Forest, they know it traveled many miles in the body of a salmon to get there.

Partnerships have been critical to the successful management of Headwaters Forest Reserve. To learn more about these partnerships, please visit: https://www.blm.gov/programs/national-conservation-land/california/headwaters-forest-reserve/partnership.