Biological Opinions - Bureau of Reclamation

augmentation will provide long-term beneficial effects by increasing spawning gravel
availability while reducing inter-gravel fine sediment concentrations.
In addition, where there is stream bank erosion, the installation of various weir structures and
wing-deflector structures will direct flow away from unstable banks and provide armor (a hard
point) to protect the toe of the slope from further erosion. Boulder faces in the deflector
structures have the added benefit of providing invertebrate habitat, and space between boulders
provides juvenile salmonid escape cover.
b. Instream Barrier Modification for Fish Passage Improvement
Instream barrier modification for fish passage improvement projects will improve salmonid fish
passage and increase access to suitable salmonid habitat. Long-term beneficial effects are
expected to result from these projects by improving passage at sites that are partial barriers, and
by providing passage at sites that are total barriers. Manual modifications to tributary mouths
may restore access for juvenile coho salmon between the mainstem and the tributaries. All of
these restoration projects will provide better fish passage.
c. Stream Bank Stabilization
Stream bank stabilization projects will reduce sedimentation from watershed and bank erosion,
decrease turbidity levels, and improve water quality for coho salmon over the long-term.
Reducing sediment delivery to the stream environment will improve fish habitat and fish survival
by increasing fish embryo and alevin survival in spawning gravels, reducing injury to juvenile
salmonids from high concentrations of suspended sediment, and minimizing the loss of quality
and quantity of pools from excessive sediment deposition. Successful implementation of stream
bank stabilization projects will offset the increased sediment delivery into streams from other
activities. In addition, streambank restoration activities will likely restore native riparian forests
or communities, provide increased cover (large wood, boulders, vegetation, and bank protection
structures) and a long-term source of all sizes of instream wood. Since no riprap or gabions are
including in the proposed stream bank stabilization, the effects of the stream bank stabilization
are expected result in long term benefits to coho salmon critical habitat in the action area.
d. Fish Passage Improvement at Stream Crossings
Thousands of dilapidated stream crossings exist on roadways throughout the coastal drainages of
northern and central California, many preventing listed salmonids from accessing vast expanses
of historic spawning and rearing habitat located upstream of the structure. In recent years, much
attention has been focused on analyzing fish passage at stream crossings through understanding
the relationship between culvert hydraulics and fish behavior (Six Rivers National Forest
Watershed Interaction Team 1999). Most juvenile coho salmon spend approximately one year in
freshwater before migrating to the ocean. Thus, juvenile coho salmon are highly dependent on
stream habitat.
Juvenile salmonids often migrate relatively long distances (i.e., several kilometers) in response
to: 1) changes in their environment (e.g., summer warming or pollution events), 2) changes in
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