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

level consequences. Land use and crop type data indicate that, while not a major agricultural
center, the CC Chinook will be exposed to all three a.i.s. We expect that exposure to methomyl
may lead to individual fitness consequences, but not to an extent that would affect population
growth rates. The risk to this species’ survival and recovery from the stressors of the action is
high for carbaryl and carbofuran, but low for methomyl.
Central Valley Spring­run Chinook Salmon
The CV Spring-run Chinook salmon ESU includes four populations of Spring-run populations in
the upper Sacramento River and its tributaries. The distribution within the Sacramento River
basin is now mostly restricted to accessible areas below dams in the mainstem river and in three
of its tributaries: Deer, Mill, and Butte Creeks. Abundance remains far below the estimated
700,000 once entering the Sacramento-San Joaquin Rivers system. The number of Spring-run
Chinook salmon spawning in the Sacramento River has averaged about 9,800 annually since
2000. While most populations within the ESU are at or above replacement, the Sacramento
River population has been steadily decreasing.
The major threats to this ESU identified in the Status of Listed Resources and Environmental
Baseline sections include impaired or loss of habitat, predation, contamination, and water
management. Reservoir dams in the Sacramento River have prevented the ESU from using its
historic spawning locations. Physical channel habitat has been altered through sediment input
from mining, levee construction, and removal of riparian vegetation for levee maintenance.
Detected pesticides in the Sacramento River include thiobencarb, carbofuran, molinate, simazine,
metolachlor, and dacthal, chlorpyrifos, carbaryl, and diazinon. State and federal water diversions
in the south Sacramento-San Joaquin Delta (Delta) have resulted in increased mortality through
prolonged migration and entrainment at the water diversion facilities. We also expect that
application of other AChE inhibiting pesticides will co-occur with carbaryl, carbofuran, and
methomyl in the waters within the ESU and exacerbate adverse effects from AChE inhibition.
With the high density of agriculture in the Sacramento River valley and the Sacramento-San
Joaquin Delta (Delta), application of all three a.i.s is expected. Large urban centers occur along
the Sacramento River and San Francisco Bay. Young and adult migrating Chinook salmon are
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