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US Fish & Wildlife Service FieldNotes

Stockton FWO: Anadromous Fish Restoration Program (AFRP) Enhances Passage and Habitat in the Cosumnes, Mokelumne, and Merced Rivers

Region 8, December 1, 2010
The Rooney Brothers Dam in the Cosumnes River prior to (top) and after (bottom) construction of the boulder weir fishway.
The Rooney Brothers Dam in the Cosumnes River prior to (top) and after (bottom) construction of the boulder weir fishway. - Photo Credit: n/a
Placement of spawning gravel in the Merced River.
Placement of spawning gravel in the Merced River. - Photo Credit: n/a

By Ramon Martin, Donnie Ratcliff, Michelle Workman, and Zachary Jackson


The U.S. Fish and Wildlife Service’s Anadromous Fish Restoration Program (AFRP), completed one fish passage project in the Cosumnes River and placed approximately 14,938 cubic yards of gravel in the Mokelumne and Merced rivers in 2010. Improving the opportunity for adult anadromous fish to reach their spawning habitats in a timely matter and improving habitat for all life stages of anadromous fish are highly important objectives of the AFRP and are crucial components in the maintenance and restoration of aquatic species and their habitats.

The Cosumnes River has 34 miles of historic anadromous fish habitat that supported large runs of Chinook salmon. Many water diversion and groundwater recharge dams were built in the Cosumnes River to help meet the agricultural water needs of the region. The Cosumnes River Passage Improvement Project was funded by AFRP in FY09 to improve fish passage at these diversion dams. The Rooney Brothers Diversion Dam was the last significant barrier without a fishway in the Cosumnes River. The project improved passage at this migration barrier by constructing a four-tiered boulder weir fishway. Final placement of the boulder weirs was completed in 2010 and post-project monitoring documented over 700 adult Chinook salmon migrating upstream through the fishway. AFRP partnered with Fishery Foundation of California, Omochumne-Hartnell Water District, Robertson-Bryan, Inc., and California Department of Fish and Game (CDFG) to successfully implement this project.

In 2010, the AFRP also improved spawning habitat in the Mokelumne and Merced rivers. Construction activities during the summer of 2010 included placement of approximately 4,166 yds3 of gravel in the Mokelumne River and 10,772 yds3 of coarse sediment for spawning habitat in the Merced River. The Mokelumne River Spawning Habitat Improvement Project area is rigorously characterized and monitored each year for spawning activity, bed form, and function. Additionally, this effort serves as a foundation project for the development of the Spawning Habitat Integrated Rehabilitation Approach (SHIRA) currently being developed and refined by the University of California, Davis. This year over 70 Chinook salmon redds were documented in the gravel enhanced area of the Mokelumne River.

The Merced River Ranch Floodplain Enhancement Project was initiated this year and once fully implemented, up to 6 acres of riparian floodplain and 1.23 miles of spawning habitat will be restored. The coarse gravel that was processed, sorted, and placed in 2010 was the first of a larger three year project where gravel additions and other habitat improvements will be completed in the Merced River. The AFRP is collaborating with Santa Fe Aggregates, Inc., Merced Irrigation District, CDFG, CALFED Ecosystem Restoration Program, and the California Department of Water Resources for the restoration projects in the Merced River and with the East Bay Municipal Utility District in the Mokelumne River.

Contact Info: Ramon Martin, 209-334-2968 ext. 401, ramon_martin@fws.gov