Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Coho Salmon: Effects of the Proposed Action on Coho Salmon
The range of ocean survival had a dramatic effect on the simulated smolt
production. Smolt production rose sharply by over 300 percent if survival was
held at the 75 percentile and dropped sharply by approximately 85 percent if
survival was held at the 25 percent level (Figure 3-34 and Figure 3-35).
Again, these steady-state simulations represent extremes that would not occur (10
straight years at the 25 or 75 percentiles), but they illustrate why coho salmon
populations undergo large variations in abundance. These simulations also
demonstrate how rapidly the populations can rebound from depressed abundance
to high abundance when ocean survival turns favorable. It is noted that the
simulations in Figure 3-35 represent a worst case freshwater condition of 90
percent exceedence flows at IGD (Proposed Action operations) combined with
2001 meteorological and tributary flow. This simulation suggests that the
population could withstand 10 straight years of worst case freshwater conditions
combined with 10 straight years of poor ocean conditions.
Figure 3-34. Total simulated smolt production over time under low (2.0 percent), medium
(4.0 percent), and high (7.5 percent) marine survival rates using proposed 90 percent
exceedence flows at IGD combined with 2001 meteorological and tributary flow data.
Proposed 90% Exceedence Flows, 2001
Simulated smolt production (thousands)
300
250
200
150
100
50
0
Marine survival
2.0%
4.0%
7.5%
1 2 3 4 5 6 7 8 9 10 11 12
Simulation year
270