Biological Opinions - Bureau of Reclamation

CDFW’s Restoration Manual (Flosi et al. 2010) to maximize the benefits of each project while
minimizing effects to salmonids. Most restoration projects are for the purpose of restoring
degraded salmonid habitat and are intended to improve instream cover, pool habitat, spawning
gravels, and flow levels; remove barriers to fish passage; and reduce or eliminate erosion and
sedimentation impacts. Others prevent fish injury or death, such as diversion screening projects.
Although some habitat restoration projects may fail or cause small losses to the juvenile life
history stage of listed salmonids in the project areas during construction, most of these projects
are anticipated to restore coho salmon habitat over the long-term.
The Restoration Manual (Flosi et al. 2010) provides design guidance and construction techniques
that facilitate proper design and construction of restoration projects. As discussed earlier in the
Effects to SONCC Coho Salmon ESU Critical Habitat section (i.e., section 11.4.2.3), NMFS
expects the habitat restoration activities will amount to an annual average of about 71 percent
effectiveness.
a. Instream Habitat Improvements
In addition to the habitat benefits discussed earlier in the Effects to SONCC Coho Salmon ESU
Critical Habitat section (i.e., section 11.4.2.3), stream enhancement techniques aimed at
reducing juvenile displacement downstream during winter floods and at providing deep pools
during summer low flows could substantially increase stream rearing capacity for coho salmon
(Narver 1978). Presence and abundance of LWD is correlated with growth, abundance and
survival of juvenile salmonids (Fausch and Northcote 1992, Spalding et al. 1995). Weir
structures can also be used to replace the need to annually build gravel push up dams. Once
these weir structures are installed and working properly, construction equipment entering and
modifying the channel would no longer be needed prior to the irrigation season. The benefits of
reducing or eliminating equipment operation during the early spring reduces the possibility of
crushing salmon redds and young salmonids.
b. Instream Barrier Modification for Fish Passage Improvement
Fish passage improvements will increase access for coho salmon adults and juveniles to
previously unavailable habitat. These restoration activities will likely increase the current spatial
structure of coho salmon populations. Reintroducing listed salmonids into previously
unavailable upstream habitat will also likely increase reproductive success and ultimately fish
population size in watersheds where the amount of quality freshwater habitat is a limiting factor.
c. Stream Bank Stabilization
In addition to the habitat benefits discussed earlier in the Effects to SONCC Coho Salmon ESU
Critical Habitat section (i.e., section 11.4.2.3), stream bank stabilization will reduce sediment
delivery to the stream and is likely to improve coho salmon embryo and alevin survival in
spawning gravels and reduce injury to juvenile coho salmon from high concentrations of
suspended sediment. Successfully reducing streambank erosion will be beneficial to coho
salmon because coho salmon will then be exposed to lower suspended sediment concentrations.
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