Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Coho Salmon: Effects of the Proposed Action on Coho Salmon
Figure 3-33. Percentage change in simulated smolt production from historical flows at
IGD (1961 to 2006) to proposed flows (modeled 2008 to 2018) by population for the 2004
water year type.
2004 Water Year Type
35.0%
Percentage change in smolt
production from baseline
30.0%
25.0%
20.0%
15.0%
10.0%
5.0%
0.0%
-5.0%
Upper
Klamath
Shasta Scott Middle
Klamath
Salmon Trinity Lower
Klamath
Flow Exceedence
90%
80%
70%
60%
50%
40%
Population
The effects of environmental uncertainty were examined on smolt production by
modeling the smolt production between 10 years of extended high, medium, and
low ocean survival, and also with dry and average hydrologic conditions. In order
to obtain an appropriate range of ocean survivals for Klamath River coho salmon,
the percentile distribution of smolt-to-adult survival rates were determined for
coho salmon released from Iron Gate Hatchery for the 1976 to 2002 brood years.
These data are described in the Life-Cycle Model Report (Appendix 3-B), and in
Cramer Fish Sciences 2007, Technical Memorandum 3. Ocean survival for Iron
Gate Hatchery coho salmon has varied from a 25 percentile value of 2.1 percent
to a 75 percentile valued of 7.6 percent (Table 3-25). The default ocean survival
rate used in all simulations, unless specified otherwise, is 4 percent.
Table 3-26. Percentiles of smolt-to-adult survivals for natural-origin Klamath River coho
salmon based on return rates of coho salmon released from Iron Gate Hatchery, 1976 to
2002 broods.
Percentile
Survival
10% 0.88%
25% 2.1%
50% 3.8%
75% 7.6%
90% 9.32%
Source: Figure 1, Cramer Fish Sciences 2007 Technical Memorandum 3
and assuming wild fish survival is double that of hatchery fish.
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