Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

In the most recent five-year geometric mean (1997 to 2001), spawning escapements were
273 for the Wenatchee population, 65 for the Entiat population, and 282 for the Methow
population. These numbers represent only 8% to 15% of the minimum abundance
thresholds. However, escapement increased substantially in 2000 and 2001 in all three
river systems. Based on 1980-2004 returns, the average annual population growth rate,
lambda, for this ESU is estimated at 0.93 (meaning the population is not replacing itself)
(Fisher and Hinrichsen 2006). Assuming that population growth rates were to continue at
1980-2004 levels, UCR spring-run Chinook salmon populations are projected to have
very high probabilities of decline within 50 years. Population viability analyses for this
species suggest that these Chinook salmon face a significant risk of extinction: a 75 to
100% probability of extinction within 100 years (given return rates for 1980 to present).
Finally, the Interior Columbia Basin Technical Recovery Team (ICBTRT) characterizes
the diversity risk to all UCR spring Chinook populations as “high”. The high risk is a
result of reduced genetic diversity from homogenization of populations that occurred
under the Grand Coulee Fish Maintenance Project in 1939-1943. Straying hatchery fish,
and a low proportion of natural-origin fish in some broodstocks and a high proportion of
hatchery fish on the spawning grounds have also contributed to the high genetic diversity
risk.
Critical Habitat
Critical habitat was designated for this species on September 2, 2005 (70 FR 52630).
Designated critical habitat includes all Columbia River estuarine areas and river reaches
proceeding upstream to Chief Joseph Dam and several tributary subbasins. The critical
habitat designation for this ESU also identifies PCEs that include sites necessary to
support one or more Chinook salmon life stages. Specific sites include freshwater
spawning sites, freshwater rearing sites, freshwater migration corridors, nearshore marine
habitat, and estuarine areas. The physical or biological features that characterize these
sites include water quality and quantity, natural cover, forage, adequate passage
conditions, and floodplain connectivity. The UCR spring-run Chinook salmon ESU has
31 watersheds within its range. Five watersheds received a medium rating and 26
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