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

spring Chinook salmon populations reach the mainstem migration corridor as yearlings, some
juvenile Chinook salmon in the lower Willamette River are sub-yearlings (Friesen, Vile et al.
2004). Off-channel habitats within the Willamette Valley floodplain are particularity important
for rearing fry and are actively being identified, reconnected and restored. We expect fry to be
exposed to the three insecticides when applications overlap with fry occurrence and will further
depress abundances of the available prey.
Based on land use and the life history of UWR Chinook salmon, we expect that this ESU will be
compromised by reduced lambdas of affected populations. The risk to this species’ survival and
recovery from the stressors of the action is high for carbaryl, carbofuran, and methomyl.
Columbia River Chum Salmon
This ESU includes two remaining populations of 16 historical populations in the lower reaches
(the Lower Gorge tributaries and Grays River) of the Columbia River. Thus, about 88% of the
historic populations are extirpated or nearly so. In the early 1900s, the run numbered in the
hundreds of thousands to a million returning adults. The size of the Lower Gorge population is
estimated at 400-500 individuals, down from a historical level of greater than 8,900 (Good,
Waples et al. 2005). Previous estimates of the Grays River population range from 331 to 812
individuals. However, the population increased in 2002 to as many as 10,000 individuals (Good,
Waples et al. 2005). Overall, the lambda values indicate a long-term downward trend at 0.954
and 0.984, respectively.
The major threats to this ESU identified in the Status of Listed Resources and Environmental
Baseline sections are hydromodification and habitat loss. Of the salmonids, chum salmon are
most averse to negotiating obstacles in their migratory pathway. Thus, they are more highly
impacted by the Columbia River hydropower system – specifically the Bonneville Dam
(Johnson, Grant et al. 1997). The water quality in the lower Columbia River is poor. Recent
USGS studies have demonstrated the presence of 25 pesticide compounds in surface waters,
including carbaryl (Ebbert and Embry 2002). Although the habitat restoration project for the
Grays River will likely provide some benefit to the population, we are unable to quantify the
overall net effect for salmonids at this time.
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