Biological Opinions - Bureau of Reclamation

Potential
Stressor
Disease
(C. shasta)
Project
Effects
Increased
likelihood of
impaired
growth,
swimming
performance,
body
condition,
and increased
stress and
susceptibility
to secondary
infections
Increased
likelihood of
diseaserelated
mortality
Life
Stage
Fry
Parr
Smolts
Fry
Parr,
and
Smolts
General
Time
April to mid-
June
April to
August
April to June
May to mid-
June
May to June
Mainstem
Location
Klamathon
Bridge (RM
187.6) to
Orleans (RM
59)
Trees of
Heaven (RM
172) to Seiad
Valley (RM
129)
Minimization Measure(s)
Flow variability will increase mainstem flows
when precipitation and snow melt is occurring
in the Upper Klamath Basin, which will help to
dilute actinospore concentrations and/or disturb
polychaetes and their habitats. In addition,
flow variability will provide dynamic fluvial
environments in the mainstem Klamath River
that may impair polychaete fitness,
reproductive success, or infection with C.
shasta. Compared to observed POR
conditions, the Project will increase the
magnitude and frequency of peak flows, which
will likely decrease the abundance of
polychaetes in the spring and summer
following a channel maintenance flow event.
In addition, the increase in magnitude and
frequency of channel maintenance flows under
the proposed action will likely decrease the
actinospore concentrations relative to the
observed POR when the channel maintenance
flow event occurs in the spring, particularly in
May and June. The adaptive management
element of the proposed action is likely to
minimize disease risks to coho salmon during
average to below average water years if EWA
surplus volume is available. Lastly the
proposed minimum daily flows in April to June
will limit the increase in disease risks posed to
coho salmon under the proposed action.
Proposed Action Effects
The proposed action will
result in disease risks to coho
salmon that are lower than
observed POR conditions yet
higher than under natural
flow conditions.
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