Biological Opinions - Bureau of Reclamation

The proposed action will have no effect on water quality in the tributaries to UKL within LRS
and SNS critical habitat because these areas are upstream of the Project, except near the
confluence of the tributaries with UKL where there is influence of lake management. Therefore,
water management by the Project will only affect the lower-most reaches of the Williamson and
Wood Rivers that are influenced by UKL elevations. However, as stated previously, USFWS
finds there are no casual links between Project operations and water quality.
9.3.1.1.2 Effects to PCE 2: Spawning and Rearing Habitat
The proposed action will have no effect on sucker critical habitat in the tributaries to UKL with
respect to its capability to adequately support sucker migration and spawning habitats that are
essential to the recovery of these species. All known spawning sites are upstream of the reaches
of these rivers affected by UKL elevations.
Implementation of proposed Project operations over the term of this BiOp (10 years) is likely to
create higher than natural surface water elevations in UKL in the spring as a result of water
storage. These water levels are likely to support extensive amounts of moderate to high-quality
sucker spawning, rearing, and foraging habitat that will facilitate the annual production of
millions of sucker eggs, embryos, larvae, and age-0 juveniles. This aspect of proposed Project
operations is likely to provide significant beneficial effects to the recovery- support function of
critical habitat for the LRS and the SNS in UKL.
However, modeling of the proposed action shows that there could be years when water levels are
so low that it could negatively affect the ability of spawning habitats to support the recovery
function of critical habitat for the LRS and the SNS in UKL. As was discussed in section 7.10,
sucker spawning and larval rearing habitat is likely to be greatly reduced only at the lowest lake
levels and those elevations occurred only once in 31 modeled years, and thus they are unlikely to
occur during the term of this BiOp. Similarly, adverse effects to larval rearing habitats are
unlikely because the elevations at which adverse effects only occur at a frequency of one in 31
modeled years, and thus are unlikely to occur during the term of this BiOp.
In August and early September, rearing habitat for age-0 juveniles, primarily for SNS because
they are more shoreline-oriented than LRS, could be reduced by the proposed action to the point
where it is likely to have adverse effects. Although there is no definitive information regarding
the fate of the affected age-0 juveniles that are displaced by draw-down operations during the
late summer, it is reasonable to assume that their fitness and survival are likely reduced due
perhaps to the lesser abundance of preferred prey species and perhaps increased exposure to
predatory, introduced fishes that are abundant in UKL. Age-0 juveniles must avoid predators
and have access to abundant high-quality food to grow and survive through the winter when they
are less active and food is less plentiful. In most years there is unlikely to be a substantial
reduction in age-0 juvenile habitat, but in about 13 percent of the years, age-0 juvenile habitat
will be substantially affected. Thus, although the adverse effects to age-0 juvenile habitat are
infrequent, the recovery-support function of critical habitat for the LRS and the SNS in UKL is
unlikely maintained in 13 percent of years.
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