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

carbofuran application to potatoes, nursery stock, sugar beets, and watermelons. Based on the
crop types, we expect that carbaryl and methomyl are commonly applied in the Lewis River
subbasin throughout the growing season and within urban and residential areas throughout the
entire year for carbaryl. Existing stocks of carbofuran are also expected to be applied throughout
the growing season. Thus, DPS exposure to these pesticides is likely.
This DPS includes winter- and summer-run types. Summer-run steelhead return to freshwater
between May and November. They enter the Columbia River in a sexually immature condition
and require several months in freshwater before spawning. Winter-run steelhead enter
freshwater from November to April. These fish are close to sexual maturation and spawn shortly
after arrival in their natal streams. Steelhead fry typically rear in off-channel habitats associated
with their natal rivers and streams for more than a year. Given this duration, juveniles are likely
to experience pesticide exposure.
Given the life history of LCR steelhead, we expect the proposed uses of carbaryl, carbofuran,
and methomyl pesticide products may contaminate rearing habitats and lead to individual fitness
and subsequent population-level consequences. The risk to this species’ survival and recovery
from the stressors of the action is high for carbaryl, carbofuran, and methomyl.
Middle Columbia River Steelhead
The MCR steelhead DPS includes 19 populations in Oregon and Washington subbasins upstream
of the Hood and Wind River systems to and including the Yakima River. Historical run
estimates for the Yakima River imply that annual species abundance may have exceeded 300,000
returning adults (Busby, Wainwright et al. 1996), whereas only 1,000 – 4,000 currently spawn.
The most recent 10-year period indicated trends in abundance were positive for approximately
half of the independent populations and negative for the remainder. Growth rates ranged from
0.97 to 1.02. Two historical populations are considered extinct.
Agricultural development is high within the range of MCR steelhead. Based on crop types and
allowable uses, we expect that carbaryl and methomyl are commonly applied in the Yakima
River basin, Walla Walla River basin, Deschutes River basin, and the John Day River basin
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