Biological Opinions - Bureau of Reclamation

Table 8.5 UKL end-of-month elevations (in ft), April through July, at the 5 to 50 percent probability levels
based on KBPM modeling of the proposed action using POR data (Reclamation 2012, Table 7-2).
Probability April May June July
(Percent)
5 4,142.5
(1,262.6 m)
4,142.3
(1,262.6 m)
4,141.4
(1,262.3 m)
4,140.1
(1,261.9 m)
10 4,142.6
(1,262.7 m)
4,142.5
(1,262.6 m)
4,141.5
(1,262.3 m)
4,140.4
(1,262.0 m)
15 4,142.8
(1,262.7 m)
4,142.7
(1,262.7 m)
4,141.7
(1,262.4 m)
4,140.5
(1,262.0 m)
20 4,143.0
(1,262.8 m)
4,142.7
(1,262.7 m)
4,141.8
(1,262.4 m)
4,140.5
(1,262.0 m)
25 4,143.1
(1,262.8 m)
4,142.8
(1,262.7 m)
4,141.9
(1,262.5 m)
4,140.7
(1,262.1 m)
30 4,143.2
(1,262.8 m)
4,142.9
(1,262.8 m)
4,142.0
(1,262.5 m)
4,140.7
(1,262.1 m)
35 4,143.2
(1,262.8 m)
4,142.9
(1,262.8 m)
4,142.0
(1,262.5 m)
4,140.8
(1,262.1 m)
40 4,143.2
(1,262.8 m)
4,142.9
(1,262.8 m)
4,142.1
(1,262.5 m)
4,140.9
(1,262.1 m)
45 4,143.3 4,143.0 4,142.1 4,140.9
(1,262.9 m)
50 4,143.3
(1,262.9 m)
(1,262.8 m)
4,143.0
(1,262.8 m)
140
(1,262.5 m)
4,142.1
(1,262.5 m)
(1,262.1 m)
4,140.9
(1,262.1 m)
Based on the analysis presented above, the USFWS concludes that, as proposed, Project
operations in most years are likely to adequately provide for inundation of emergent vegetation
that is very important as larval sucker habitat during the April-July period. During those years
the conservation needs of the LRS and SNS populations in UKL are likely to be met. However,
when lake levels go below 4,140.0 ft (1,261.9 m) at the end of July, substantial reductions of
larval habitat are likely to occur and are likely to reduce larval productivity or survival.
However, such events are likely to be rare with implementation of Project operations based on
modeling of the POR because such conditions occurred in only one year out of 31 modeled
years. 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.
The modified proposed action, mentioned above in Sections 4 and 8.3.1.1, will not affect larval
habitat because UKL elevations will not be altered, or would not result in an adverse effect to
LRS and SNS greater than what was analyzed here.
8.3.1.4 Effects to Age-0 Juvenile Habitat in UKL
Sucker larvae transform into age-0 juveniles typically by late July, and they utilize a variety of
shallow-water areas that are usually less than 3 ft deep (Buettner and Scoppettone 1990,
Terwilliger 2006). As they grow, age-0 juveniles move offshore, especially LRS juveniles,