Biological Opinions - Bureau of Reclamation

Based on our review of the literature cited above, the USFWS concludes that the past pattern of
age-0 juvenile sucker departure from near-shore areas in late September when the UKL surface
elevation is nearing its annual minimum is not likely caused by Project operations, and instead is
likely a natural behavior related to growth. However, declines in the amounts and diversity of
age-0 juvenile habitats in August and early September are more likely to have adverse effects on
juvenile suckers as discussed above.
The absolute minimum daily elevation, according to the KBPM outputs for the proposed action
based upon the POR, is 4,137.72 ft (1,261.18 m) in early October. The BA states that
Reclamation does not intend to go below 4,137.50 ft (1,261.11 m) in UKL (USBR 2012, p. 4-
26). This elevation is outside of what was modeled by KBPM and, therefore, we have no way to
assess its effects on the LRS and the SNS. Additionally, the effects of a 4,137.50 ft (1,261.11 m)
minimum elevation in UKL were not analyzed by Reclamation. In summary, we were only able
to analyze those conditions predicted by KBMP, based on the POR, so any daily UKL elevation
below 4,137.72 ft (1,261.18 m) would be outside the scope of effects analyzed under this BiOp.
As discussed above, there is uncertainty regarding the effects of proposed Project operations to
LRS and SNS age-0 juveniles caused by declining water levels in August and early September.
However, to the degree that diverse, shallow-water habitats confer benefits to LRS and SNS age-
0 juveniles, the loss of that habitat is likely to cause adverse effects. However, such events are
likely to be rare with implementation of Project operations based on modeling of the POR: UKL
elevation at or below 4,139.0 ft (1,261.6 m) occurred in 4 of 31 modeled years (13 percent of
modeled years) during August. Taking into account that adult LRS and SNS are long-lived fish,
such rare events are not likely to represent a significant limiting factor to persistence of LRS and
SNS populations at UKL. However, the lack of recruitment into the adult breeding population of
both species in UKL since the late 1990s is magnifying the significance of those adverse effects
even though such events are likely to be infrequent.
As discussed above, there is uncertainty regarding what the effects are to LRS and SNS age-0
juveniles of the declining water levels in August and early September resulting from the
proposed action. However, to the degree that diverse, shallow-water habitats confer benefits to
LRS and SNS age-0 juveniles, the loss of that habitat is likely to cause adverse effects.
However, such events are likely to be rare with the implementation of proposed Project
operations based on modeling of the POR: UKL elevations at or below 4,139.0 ft (1,261.6 m)
occurred in 4 of 31 modeled years during August. Taking into account that adult LRS and SNS
are long-lived fish, such rare events are not likely to represent a significant limiting factor to
persistence of LRS and SNS populations at UKL. However, the lack of recruitment into the
adult breeding population of both species since the late 1990s is magnifying the significance of
those adverse effects even though such events are likely to be uncommon.
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