Biological Opinions - Bureau of Reclamation

Creek, and includes Willow, Fourmile, and Wildhorse Creeks in California, and Willow Creek to
its East Fork in Oregon (77 FR 73740).
9.3.2.1 Effects to LRS and SNS Critical Habitat at Clear Lake and in Willow Creek
9.3.2.1.1 Effects to PCE 1—Water
At Clear Lake, the proposed action is not likely to affect water quality except at the lowest lake
levels (discussed in Section 8.3.5 in more detail). However, water quality monitoring over a
wide range of lake levels and years documented water quality conditions that were adequate for
sucker survival during most years (USBR 1994, 2001a, 2007). Although low water levels could
result in degraded water quality, particularly higher temperatures, and lower DO concentrations
(USFWS 2008), the conditions have been within the range that is tolerated by suckers and
therefore are not a limiting factor for persistence of SNS and LRS in Clear Lake. Therefore, the
USFWS finds that proposed Project operations at Clear Lake are not likely to adversely affect
water quality necessary to adequately support recovery of the LRS and the SNS. Thus, the
proposed action in Clear Lake is likely to provide the necessary recovery-support function of
critical habitat for the LRS and the SNS for water quality.
9.3.2.1.2 Effects to PCE 2—Spawning and Rearing Habitat
Access to spawning habitat in Willow Creek, which is the only know habitat used for spawning
by suckers in Clear Lake, appears to be mostly dependent on Willow Creek flows, as discussed
in Section 8.3.5 thus the effects of lake levels from the proposed action on spawning habitat
component of PCE2 are thought to be minimal. Taking into account that adult LRS and SNS are
long-lived fish and that the proposed action is unchanged from past operations, the proposed
Project operations should provide sufficient access to spawning habitat for spawning to occur at
a frequency which will be sufficient to maintain a diverse age-class structure and will result in
sufficient adults to maintain resiliency. Thus, proposed Project operations are not likely to
represent a significant limiting factor for migration and spawning success at Clear Lake.
The proposed action is likely to provide adequate rearing habitat for all sucker life stages in
Clear Lake except during droughts when both water depth and surface area contracts, therefore
affecting components of PCE 2. The amount of habitat in Clear Lake is highly variable because
inflows to Clear Lake are characterized by multiple low-inflow years punctuated by less frequent
high inflow years. Additionally, evaporation and leakage are high because of the shallow depths
and large surface area of the lake. At the lowest lake levels under the proposed action, water
depths in the west lobe are so low that suckers could get stranded and would be vulnerable to
pelican predation. Those conditions are likely to occur once during the proposed action because
they occurred in the POR at a frequency of 5 to10 percent. The minimum proposed Clear Lake
elevations will likely provide adequate protection from drought in most years, but extended
drought will result in a significant reduction in lake area and depth. Thus, the proposed action is
likely adversely affecting rearing habitat during droughts that are likely to occur once during the
term of this BiOp.
Although there are adverse effects to this PCE, negative impacts to the recovery role of the
component of critical habitat in Clear Lake are not anticipated. The minimum lake elevation
being proposed for Clear Lake (i.e., 4,520.6 ft) has not changed from minimums previously
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