Biological Opinions - Bureau of Reclamation

outside those that described and analyzed in Reclamation’s BA because of the following
factors. To ensure that the revised minimum flows do not change the modeled UKL elevations,
Reclamation will either delay the start of Project irrigation deliveries from UKL or will limit
discretionary diversions from the lake by an equivalent amount to the increased releases at Link
River Dam to avoid adversely impacting UKL elevations and ESA-listed suckers. Furthermore,
Reclamation has assessed the potential impacts to UKL and found that lake levels are expected
to be slightly higher for portions of the March through June period when a delay of the start of
irrigation deliveries is implemented. This would occur because the model used to develop the
Proposed Action assumed that Project deliveries would begin on March 1.
Additionally, Reclamation stated they may increase Link River flows during the April through
June period to reduce coho salmon parasite concentrations in the river. The magnitude and
duration of the flow increase will be developed with consideration to (a) an effective dilution
factor, (b) surplus EWA volume, and (c) potential effects to UKL and ESA-listed
suckers. Within 24 hours of consultation with the FASTA Team, Reclamation will implement
the flow increase at Link River, if appropriate based on discussions the FASTA and the Services.
A deviation from the formulaic distribution of EWA could result in short term effects to UKL
elevations. In the event that a deviation from the formulaic distribution of EWA is expected to
result in effects to UKL elevations throughout the spring/summer period, the FASTA Team will
closely coordinate with the USFWS to ensure that the deviation will not create adverse effects
greater than analyzed by USFWS. The expected end of September UKL elevation should remain
unchanged as no increase to EWA will occur as a result of this change in EWA distribution.
8.3.1.2 Effects of the Proposed Action to LRS and SNS Embryo and Larval Pre-swim-up
Habitat at Shoreline Springs in UKL
LRS embryos and pre-swim-up larvae are expected to be present in the gravel at the shoreline
springs for approximately 3 weeks following spawning and fertilization (Perkins and
Scoppettone 1996). Thus, LRS eggs fertilized in late April would be in the spawning gravel in
mid-May, and any eggs fertilized in late May would still be present in the gravel in mid-June. If
embryos or larvae are exposed to the air they will die from desiccation, so adverse effects could
result from drawing the lake down too soon in the spring, exposing embryos or larvae. Although
we do not know exactly at what elevation habitat for embryos and per-swim-up larvae becomes
negatively affected, we assume those effects begin occurring when elevations in June go below
4,142.0 ft (1,262.5 m). That assumes some fertilized eggs were deposited earlier when lake
levels were at near 4,143.0 feet (1,262.8 m) and at a substrate elevation of 4,142.0 ft (1,262.5 m).
Exposure of embryos and pre-swim-up larvae to air is most likely to occur in June because lake
levels could drop up to 1 ft (0.3 m) from May elevations (Table 8.2). That exposure is expected
to occur in about 30 percent of future water years based on the POR (Table 8.5). Furthermore,
the lower lake levels drop in June, the greater these effects are likely to be. However, although
the loss of sucker embryos and larvae is an adverse effect to the LRS and the SNS, best available
information on larval production in past years of Project operations supports a finding that
implementation of proposed Project operations, which are likely to cause higher minimum lake
elevations than in the past with more certainty that the minimum modeled lake elevations will
not be exceeded, is likely to provide for the annual production of millions of LRS and SNS
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