Fish on the Move During Redwood Creek Enhancement Project

By Scientists in Parks intern Tim Smoot, San Francisco Bay Area Network Salmonid Monitoring Program

Juvenile coho salmon that was relocated out of the construction area.

NPS

September 2023 - The second phase of a major restoration project aimed at improving habitat for salmonids in Muir Woods National Monument is underway. In the 1930s, the Civilian Conservation Corps placed large bouldersalong the edges of Redwood Creek in Muir Woods—and removed woody debris —in an effort to stabilize the creek banks and prevent erosion. This was done in an attempt to protect the famous redwood trees. However, the trees did not require these changes, which disturbed natural water flow, resulting in straighter, shallower, and more uniform habitat within the creek.

Watershed Stewards Program Corpsmember Lizzie Bear holding a steelhead that’s at least one year old and was relocated out of the construction area.

NPS / Environment for the Americas / Tim Smoot

Redwood Creek is inhabited by federally endangered coho salmon (Oncorhynchus kisutch) and threatened steelhead trout (O. mykiss). As juveniles, these fishes rely on deep pools and large woody debris for cover. In an effort to support their recovery, the restoration project aims to remove the boulders from along the creek edges and install large pieces of wood. Results from the first phase of the project confirmed that these steps promote natural creek flow that meanders, create deep pools, and provide cover for the young salmonids.

The San Francisco Bay Area Network’s coho and steelhead monitoring team assisted with the restoration project by removing fish from the construction areas prior to the arrival of heavy machinery. For the large boulders to be removed and large woody debris to be installed, sections of the creek were then drained of water by diverting creek flow through large pipes.

Prior to and during the dewatering process, the fisheries team captured fish and other aquatic wildlife, including coho salmon, steelhead trout, sculpin (Cottus spp.), and California giant salamanders (Dicamptodon ensatus), and moved them to areas where the creek flow was uninterrupted. The team used seine nets and electrofisher backpacks to capture the animals in the construction areas before safely relocating them downstream. A seine net typically matches the width and depth of the stream and is used to encircle the fishes and pull them out of the water. An electrofisher temporarily stuns fish by introducing a mild electric current to the water column, allowing crew members to capture the fish with handheld dip nets.

In one of the construction areas, more than 25 coho salmon and 100 steelhead trout were successfully captured and relocated, along with over 1,100 sculpin and around 170 California giant salamanders. The team is excited to see how the salmon use these improvements in habitat through the Muir Woods section of Redwood Creek in the coming years.

Restoration crewmembers search for fish as water is pumped out of a deep pool.

NPS / Environment for the Americas / Tim Smoot

For more information

• San Francisco Bay Area Network Salmonid Monitoring webpage
• Pacific Coast Science & Learning Center Coho & Steelhead webpage
  • San Francisco Bay Area Coho and Steelhead Blog
• Contact Fishery Biologist Michael Reichmuth

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