Biological Opinions - Bureau of Reclamation

River Diversion Channel, and Ady Canal. Entrainment is also anticipated to occur at privately
owned pumps and gravity diversions that use Project water and therefore are part of the Project,
as described in the Environmental Baseline and Effects of the Action (sections 7 and 8) of this
BiOp. The amount of entrainment is expected to vary on a seasonal and yearly basis, depending
upon the level of larval production in any given year and other factors. The level of take we are
authorizing is based upon what is believed to be high production conditions, and thus should be
close to the maximum. We have made adjustments in estimated entrainment rates based on
decreases in LRS and SNS population estimates, and the assumption that entrainment is likely to
be proportional to the abundance of adult suckers, as explained below.
13.2.1.2 A Canal Entrainment Estimates
Most of the entrainment take by the Project occurs at A Canal and Link River Dam spillway
gates because these facilities are immediately downstream from UKL. Although the A Canal is
equipped with a state-of the-art fish screen that meets USFWS criteria, up to 320,000 larvae (50
percent of the 640,000 that reach the screen) pass through the screen and are entrained into the
canal every year.
We assume all of the larvae that contact the A Canal fish screen will be harassed because this
will likely disrupt normal behaviors, such as feeding and predator avoidance. Additionally, most
of the larvae that pass through the screen will be harmed because they are likely to die from
adverse water quality, passing through pumps and being discharged onto agricultural fields, or
die at the end of the irrigation season when irrigation canals are drained. However, some larvae
will survive in the canals and up to 1,500 are expected to be salvaged as age-0 juveniles at the
end of the irrigation season and will be moved to permanent water bodies, such as UKL, where
they are more likely to survive. The number of larvae and age-0 juveniles entrained into the A
Canal headworks and that subsequently pass through the screen will be highly variable annually,
and will likely depend on several factors, including annual production, which can vary annually
by several orders of magnitude (Simon et al. 2012).
Suckers larger than about 30 mm total length are not likely entrained into the A Canal because of
the small-sized openings in the screen. We estimate that up to 50,000 age-0 juvenile suckers and
80 adults (and older juveniles) could be bypassed to the river every year, based on entrainment
studies by Gutermuth et al. (2000a, b). We assume all of these suckers passing through the
bypass facility will be harassed because it will likely substantially disrupt normal behaviors, such
as feeding and predator avoidance. Additionally, it is reasonable to assume that a small
percentage of suckers (here we assume up to 1 percent) will be harmed (e.g., become injured) in
the process of moving through the A Canal by-pass facility. Thus, we assume up to 500
juveniles and 1 adult are harmed per year at the A Canal.
The above entrainment estimates were developed based on entrainment data reported by
Gutermuth (2000a, b) and the analysis presented in the 2008 Klamath Project BiOp (USFWS
2008), with one modification. For this BiOp, we reduced the numbers of suckers likely to be
entrained by the A Canal and Link River Dam at the outlet of UKL by 80 percent because that is
the estimated amount of decline that has occurred in the total numbers of adult sucker in UKL
since the late 1990s, when entrainment was last studied (Gutermuth et al. 2000a, b). It is
reasonable to assume that fewer adults would result in fewer eggs, and fewer eggs would result
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