Biological Opinions - Bureau of Reclamation

Table 8.6 UKL end-of-month elevations (in feet), July through September, at the 5 to 50 percent probability
levels, based on KBPM modeling of the proposed action using POR data (Reclamation 2012, Table 7-4).
Probability (Percent) July August September
5 4,140.1
(1,261.9 m)
10 4,140.4
(1,262.0 m)
15 4,140.5
(1,262.0 m)
20 4,140.5
(1,262.0 m)
25 4,140.7
(1,262.1 m)
30 4,140.7
(1,262.1 m)
35 4,140.8
(1,262.1 m)
40 4,140.9
(1,262.2 m)
45 4,140.9
(1,262.2 m)
50 4,140.9
(1,262.2 m)
4,138.9
(1,261.5 m)
4,139.0
(1,261.6 m)
4,139.1
(1,261.6 m)
4,139.2
(1,261.6 m)
4,139.3
(1,261.7 m)
4,139.4
(1,261.7 m)
4,139.5
(1,261.7 m)
4,139.6
(1,261.8 m)
4,139.6
(1,261.8 m)
4,139.7
(1,261.8 m)
4,138.2
(1,261.3 m)
4,138.3
(1,261.4 m)
4,138.3
(1,261.4 m)
4,138.5
(1,261.4 m)
4,138.7
(1,261.5 m)
4,138.8
(1,261.5 m)
4,138.8
(1,261.5 m)
4,138.9
(1,261.5 m)
4,138.9
(1,261.5 m)
4,139.0
(1,261.6 m)
8.3.1.5 Effects to Habitat of Older (Age 1+) Juveniles and Adults in UKL
Radio-telemetry studies have shown that adult suckers primarily use the north end of UKL above
Bare Island from June to September (Peck 2000, Reiser et al. 2001, Banish et al. 2007, Banish et
al. 2009). During this period, adult suckers are found in open water areas of the lake, typically at
depths of greater than 9 ft (3 m), and they tend to avoid depths less than 6 ft (2 m); in general,
LRS are found farther offshore than SNS (Peck 2000, Reiser et al. 2001, Banish et al. 2009).
Note that these depths were actually measured at the location of the detected fish and are not
based on bathymetric maps that were inaccurate at that time.
During radio-tracking studies, neither LRS nor SNS adults were observed using depths less than
3 ft (1 m; Banish et al. 2007). In studies done in 2005 and 2006, LRS selected water depths
greater than 10 ft (3 m), and SNS often selected depths greater than 6 ft (2 m; Banish et al. 2007,
Banish et al. 2009). Adult suckers were mostly located at water depths greater than the mean
depth available in the area of the lake where they occur, which suggests they were actively
selecting for relatively deep water, but the data do not indicate where the fish are distributed
through the water column. However, neither species was found at depths greater than 25 ft (8 m;
Banish et al. 2007). Depths up to about 40 feet (12 m) or more occur along the east side of Eagle
Ridge.
In the 2008 BiOp (USFWS 2008), one of our concerns was that low lake levels during August
and September could pose a threat to adult suckers because shallow depths could reduce access
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