Restoration for Native Salmonid Conservation

Introduction

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Chinook salmon (Oncorhynchus tshawytscha) and Steelhead trout (Oncorhynchus mykiss) have complex life cycles in which they migrate between marine and freshwater environments. This process is also known as anadromy. Both species of salmonids rear within gravel substrate in freshwater streams, where they live as fry before migrating to the Pacific Ocean as smolts. As adults, they return to their natal freshwater streams to spawn. Chinook salmon die after spawning but Steelhead, which are the anadromous form of Rainbow trout, are unique in that they can spawn multiple times. 

Restoration efforts by fishery biologists and managers often focus on improving habitat conditions to restore salmonid populations. When returning to headwater streams to spawn, adult Chinook salmon and Steelhead are highly sensitive to environmental conditions including flow and temperature. In addition, female salmonids prefer certain types of in-stream gravel substrate to construct gravel nests to lay their eggs. These nests are known by fisheries biologists as redds. 

Wild Chinook salmon and Steelhead are native to the North Pacific Ocean, ranging historically from northern Alaska and Russia to southern California. A combination of overfishing,  construction of hydroelectric dams, and habitat loss from agriculture, logging, and mining have reduced their populations, especially within their current southernmost range in the Central Valley, California. As such, several subpopulations, also known as stocks, of both species are listed as Threatened or Endangered under the Endangered Species Act. Fish hatcheries produce additional juvenile salmonids to lessen impacts from upstream habitat blocked by hydroelectric dams.

The Lower American River outside of Sacramento, California supports populations of Chinook salmon and Steelhead. Historical modifications and habitat degradation from human activities such as mining, irrigation, and the construction of the Folsom Dam in 1955 reduced salmon populations. To mitigate this population decline, Nimbus Fish Hatchery in Rancho Cordova, California releases hatchery-reared fish every year.

Key Issues Addressed

The Lower American River contains threatened stocks of Chinook salmon and Steelhead. Historical dredging for gold mining and its associated gravel tailings along the river banks have caused river channelization. This has reduced the amount of suitable gravel habitat for rearing juveniles and spawning adults, which in turn reduces the number of salmonids that survive as juveniles in these conditions, as well as the number that return to spawn as adults. 

Folsom Dam further alters downstream temperatures and flow regimes of the Lower American River. The dam structure also lacks a means for fish passage fish passage
Fish passage is the ability of fish or other aquatic species to move freely throughout their life to find food, reproduce, and complete their natural migration cycles. Millions of barriers to fish passage across the country are fragmenting habitat and leading to species declines. The U.S. Fish and Wildlife Service's National Fish Passage Program is working to reconnect watersheds to benefit both wildlife and people.

Learn more about fish passage , blocking salmonid populations from returning further upstream to spawn. Returning Chinook salmon and Steelhead therefore spawn on riffle habitats at gravel sites downstream of the dam to complete their upstream migration.

Restoration projects accordingly focus on replacing suitable gravel habitat, woody material, side channels, and floodplains for both spawning and rearing Chinook salmon and steelhead in several stretches of the Lower American River downstream of the Folsom Dam. Enhancing spawning conditions through habitat restoration increases the number of successful salmon redds and provides nursery habitat for their eggs and emerging fry. A partnership between the Bureau of Reclamation, Sacramento Water Forum, and U.S. Fish and Wildlife Service is working to address these challenges.

Project Goals

• Achieve salmonid management goals through collaboration
• Restore appropriate river channel and floodplain sites for spawning and rearing in the Lower American River
• Better understand the life histories of Chinook salmon and steelhead in this system
• Maintain suitable habitat conditions for long-term salmonid conservation

Project Highlights

Recycled Rock: Rock waste along riverbanks from historic gold mining are repurposed as gravel substrate for restoration of salmonid spawning beds in the Lower American River.

• Creative Collaboration: Federal agencies, state agencies, and local municipalities collaborate to implement on-the-ground restoration and policy for conserving salmonid populations, as well as develop and implement long-term scientific studies. Due to the financial and spatial scope of these restoration efforts, these projects would not be possible without multiple collaborators to increase effectiveness through long-term research and management.
• Long-Term Partnerships: Since 2008, the partnership between Reclamation and Sacramento Water Forum has invested over $7 million into habitat restoration in the Lower American River. This has created over 30 acres of suitable habitat for spawning adults and 1.7 miles of side channels for rearing juveniles. 
• Ongoing Gravel Augmentation and Habitat Expansion. Over four weeks in September 2019, this project expanded to the Upper Sailor Bar location, excavating a new side channel and strategically placing approximately 14,000 cubic yards of washed and sorted gravel into the main channel. Construction machinery is used continually to augment and subsequently place gravel back within spawning locations before cooling temperatures trigger the fall Chinook salmon runs from October through December.
• Positive Public Reception and News Coverage: Partnership and collaboration among diverse stakeholders has been met with positive feedback from local residents and news media. Citizen working groups provide the restoration group with planning input on projects along the American River, and volunteers also help with local invasive plant removal projects in riparian riparian
  Definition of riparian habitat or riparian areas.
  
  Learn more about riparian corridors. The Water Forum also supports the local Soil Born Farms Education Program and Effie Yeaw Nature Center for youth education on aquatic ecosystems, hands-on biology labs, and the role of Sacramento’s natural and cultural resources.

Lessons Learned

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Mine tailings along the banks of the Lower American River are an excellent source for gravel spawning material. The gravel placed into the river for spawning ranges from about 1/8 inch to 4 inches in diameter with a median size of around an inch. Salmon tend to favor spawning in smaller gravel, so there is a balance between providing the smaller gravel sizes that fish can more readily navigate versus  having larger material to maintain habitat that can better withstand the impacts of high flow conditions. Projects include large cobble at the downstream ends of spawning riffles and at key locations in side channels to maintain habitat diversity. Salmon biologists have documented increased spawning activity in Sailor Bar, with zero redds counted in 2018 and between 700 and 1,100 redds after gravel augmentation in 2019.

Projects closer to the dam tend to receive greater fish use, both adult and juvenile, than projects further downstream. The American River contains a relatively short section used by anadromous fish compared to other Central Valley salmon streams. Accordingly, salmon quickly ascend to the top of the habitat at the dam, with many spawning in suitable habitat close by. The highest juvenile rearing densities are near the spawning habitat. Once the juveniles begin emigration downstream it appears they generally leave the river quickly, as opposed to remaining in rearing habitats lower in the river.

Fishery biologists have found that salmon in the Lower American River display more life history variation than previously thought. Biologists can reconstruct an adult salmon’s life history via genetic samples collected from fin clips, otolith or “inner ear stone” samples for life history and age determination, and rotary screw traps placed in the river that document timing of outmigrating juvenile fish. Biologists found that Chinook Salmon in particular show two life history patterns, fish that stay in the river for longer periods versus those that outmigrate to the ocean more quickly as juveniles. This has important conservation and management implications for how and when to implement restoration projects and policy.

Gravel augmentation also has broader ecosystem impacts, including increasing populations of macroinvertebrates that quickly colonize the fresh gravel, and the increasing presence of wildlife, e.g.,  beavers, which in turn increase the quality of restored habitat. Higher juvenile salmonid densities have been found behind beaver dams within the project locations. Additional woody debris input creates more nursery environments for young Chinook salmon and Steelhead. Doubling the amount of habitat for juvenile fish increases overall aquatic community diversity.

Habitat restoration and enhancement is an ongoing, long-term process for salmonid conservation. Restoration efforts utilize sites for projects located on Sacramento County Parks land which avoids the complications of working with multiple types of land ownership. Sites need to be revisited, especially after high flow events such floods, to replace gravel that is washed downstream. Managers have subsequently adapted by adding larger rocks for better gravel retention through the range of flow conditions.

Next Steps

• Create more juvenile rearing habitat in the Lower American River
• Replace habitat and replenish gravel as needed at previous and new restoration locations
• Improve gravel habitat utility for a range of flow conditions (match substrate channel characteristics with flow regime)
• Address other ecosystems, apply lessons learned from Lower American River restoration projects to salmonid spawning grounds with similar restoration opportunities elsewhere in the Upper Sacramento River Basin

Funding Partners

Central Valley Project Improvement Act

Resources

• CCAST Webinar September 2020
• Bureau of Reclamation News Story: Lower American River partnership celebrates new habitat restoration project to protect salmon and steelhead.
• Water Forum Article: Lower American River gravel augmentation project nurtures record number of salmon nests. 
• NOAA Fisheries Species Directory: Steelhead Trout
• NOAA Fisheries Species Directory: Chinook Salmon
• California Department of Fish and Wildlife: Nimbus Fish Hatchery
• Gohring, T. 2019. “Gravel Augmentation Update to the Recreation and Park Commission.” Presentation.The Water Forum.
• Quinn, T. 2018. The Behavior and Ecology of Pacific Salmon and Trout 2nd Edition. University of Washington Press.

Contacts

• John Hannon, Fisheries Biologist, Bureau of Reclamation: Sacramento, CA. jhannon@usbr.gov
• Lilly Allen, Scientist, Ecosystem Restoration, The Water Forum: lallen@cityofsacramento.org

Case Study Lead Author

Alex Koeberle, CART Research Specialist, University of Arizona, akoeberle@email.arizona.edu

Suggested Citation

Koeberle, A., L. (2020). “Gravel restoration for native salmonid conservation in the Lower American River of California.” CART. Retrieved from https://www.fws.gov/project/restoration-native-salmonid-conservation.