Biological Opinions - Bureau of Reclamation

populations, and contains the largest LRS population remaining within its range. This recovery
unit contains one of only three previously self-sustaining SNS populations. For these reasons,
the UKL Recovery Unit is essential for species redundancy and resiliency.
As described above, the proposed action is likely to have a variety of effects to the LRS and SNS
populations in the UKL recovery unit. Some beneficial effects of the proposed action are likely
to include: (1) water storage in winter in UKL that results in increases in spawning habitat and
young-of-the year nursery habitat in most years, and (2) lake level variations that could help
maintain marsh vegetation that requires air exposure for seedling growth.
Adverse effects to LRS and SNS populations in the UKL Recovery Unit as a result of the
proposed action are likely to include: (1) decreases in age-0 juvenile and adult habitat between
July and October; (2) increased risk of disease and bird predation for juveniles and adults at the
lowest water levels; (4) substantial entrainment of larvae and age-0 juveniles at the A Canal and
Link River Dam.
We also anticipate that adverse effects to the declining adult sucker populations in this recovery
unit as a result of Project operations will be minimized through the proposed relocation of adult
suckers to UKL from Lake Ewauna and the proposed controlled-propagation program, both of
which are discussed below.
Proposed Project operations are compatible with the annual production of millions of LRS and
SNS eggs and larvae at UKL by the sucker populations spawning in the Williamson and Sprague
Rivers. Proposed Project operations are likely to cause seasonal habitat losses at UKL affecting
embryo, larval, juvenile, and adult suckers, and entrainment of all life stages, and the
significance of those effects are magnified by the lack of recruitment into the adult breeding
populations which are aging and in decline. However, most of the adverse effects caused by
proposed Project operations to habitat for sucker spawning and early life-stages are unlikely to
occur during the 10-year term of the proposed Project operations because of the low frequency of
the lake elevations causing those adverse effects, based on modeling of the POR.
Project-related adverse effects to age-0 juveniles are more likely to occur because those lake
levels occur at a higher frequency of modeled years. Project-related habitat effects to older
juveniles and adults that use deeper water are unlikely to occur during the term of the proposed
action because of the low frequency of the lake elevations causing those effects based on
modeling of the POR. Effects of the proposed action to water quality in UKL are unlikely, but
they are more likely to occur downstream in Keno Reservoir where Project agricultural water is
discharged. However, effects coming from the Project are likely to be small relative to other
effects.
Project-related effects at UKL that are most likely to rise to a population-level are entrainment of
juvenile suckers because of the large numbers entrained and the relative importance of juveniles
in terms of likely contributing to recruitment. If there is a small level of recruitment occurring in
UKL, which is likely, then any loss of young suckers by entrainment or other actions resulting
from Project operations would reduce recruitment. Given the lack of documented recruitment
into the adult populations of the LRS and the SNS at UKL since the late 1990s, such recruitment
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