Biological Opinions - Bureau of Reclamation

11.6.3 Project Effects on Essential Habitat Types
Critical habitat for SONCC coho salmon ESU is comprised of physical and biological features
that are essential for the conservation of coho salmon, including spawning habitat, rearing
habitat, and migration corridors to support one or more life stages of SONCC coho salmon. As
summarized below, the conservation value of critical habitat in certain reaches of the Klamath
River between IGD and approximately Orleans is likely to be reduced by Project operations at
certain times or under certain environmental conditions. However, restoration activities under
the proposed action are likely to offset those reductions or enhance, in some cases, the
conservation value of critical habitat in the action area.
11.6.3.1 Spawning Habitat
The proposed action will reduce the magnitude, frequency, and duration of flows between 5,000
and 10,000 cfs relative to the natural flow regime, which will likely reduce mobilization of fines
from spawning gravel. Therefore, the proposed action is likely to reduce some quality of
spawning habitat when spawning gravel becomes filled by fines over time. While the proposed
action will likely reduce the duration, magnitude and frequency of fine sediment mobilization
from spawning gravel when IGD flows are below 10,000 cfs, adult coho salmon are able to
clean fine sediment from spawning gravel (Kondolf et al. 1993, Kondolf 2012) prior to
depositing eggs. In addition, the proposed action is not likely to result in armoring of spawning
gravel because the proposed action will have minimal reductions to the magnitude, frequency,
and duration of flows needed to mobilize armored substrates (i.e., at least approximately 10,000
cfs; Reclamation 2011b) relative to the natural hydrograph. During relatively wet years when
IGD flows are variable and incrementally increase during the late fall and winter, the proposed
action is expected to increase the quantity of spawning habitat in the mainstem Klamath River.
Therefore, NMFS expects that the quantity of coho salmon spawning habitat will be suitable
under the proposed action.
Spawning habitat is not likely to be adversely affected by the temporary increase in fine
sediment resulting from the proposed restoration activities. Restoration activities will improve
the quality of spawning habitat over the long term by reducing the amount of suspended
sediment that enters the stream through various types of erosion control. Additionally, gravel
augmentation will increase the amount of spawning habitat available.
In summary, the proposed action is likely to have minimal adverse effects to spawning habitat
quality in the mainstem Klamath River during consecutive dry water years. However, the
proposed action is likely to result in improvements to spawning habitat quality in the action area
through gravel augmentation, and sediment reduction projects.
11.6.3.2 Migratory Corridors
The proposed action is not likely to adversely affect the migratory corridor for coho salmon in
the action area. The proposed action will lower flows in the mainstem Klamath River during
much of November and December. However, the November and December flows of at least 950
cfs under the proposed action will provide the depth and velocity for coho salmon migration, and
thus, are not expected to impede adult migration. In addition, the proposed action retains some
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