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

Life History
UWR Chinook salmon exhibit an earlier time of entry into the Columbia River and
estuary than other spring Chinook salmon ESUs (Meyers, Kope et al. 1998). Although
juveniles from interior spring Chinook salmon populations reach the mainstem migration
corridor as yearling, some juvenile Chinook salmon in the lower Willamette River are
subyearlings (Friesen, Vile et al. 2004).
Status and Trends
UWR Chinook salmon were listed as threatened on March 24, 1999 (64 FR 14308), and
reaffirmed as threatened on June 28, 2005 (70 FR 37160). The total abundance of adult
spring-run Chinook salmon (hatchery-origin + natural-origin fish) passing Willamette
Falls has remained relatively steady over the past 50 years (ranging from approximately
20,000 to 70,000 fish). However, it is an order of magnitude below the peak abundance
levels observed in the 1920s (approximately 300,000 adults). Until recent years,
interpretation of abundance levels has been confounded by a high but uncertain fraction
of hatchery-produced fish.
Most natural spring Chinook salmon populations is likely extirpated or nearly so. Only
one remaining naturally reproducing population is identified in this ESU: the spring
Chinook salmon in the McKenzie River. Unfortunately, recent short-term declines in
abundance suggest that this population may not be self-sustaining (Meyers, Kope et al.
1998; Good, Waples et al. 2005). Most of the natural-origin populations in this ESU
have very low current abundances (less than a few hundred fish) and many largely have
been replaced by hatchery production. Long- and short-term trends for population
growth rate are approximately 1 or are negative, depending on the metric examined (i.e.,
long-term trend [regression of log-transformed spawner abundance] or lambda [median
population growth rate]). Although the population increased substantially in 2000-2003,
it was probably due to increased survival in the ocean. Future survival rates in the ocean
are unpredictable, and the likelihood of long-term sustainability for this population has
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