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

The major threats to this ESU identified in the Status of Listed Resources and Environmental
Baseline sections include hydromorphological changes from hydropower development, loss of
tidal marsh and swamp habitat, and reduced or eliminated access to subbasin headwaters from by
the construction of non-federal dams. LCR Chinook salmon spawning and rearing habitats in
tributary mainstems have been adversely affected by sedimentation, elevated water temperature,
and reduced habitat diversity. The survival of yearlings in the ocean is also affected by habitat
conditions in the estuary, such as changes in food availability and the presence of contaminants.
NAWQA sampling in surface waters within the ESU range detected more than 50 pesticides in
streams. Concentrations of ten pesticides, including carbaryl and carbofuran, also exceeded
EPA’s chronic toxicity aquatic life criteria (Wentz, Bonn et al. 1998). The combined impacts
from these multiple threats continue to affect this ESU.
Most of the highly developed land and agricultural areas in this ESU’s range are adjacent to
salmonid habitat. Registered uses of carbaryl, carbofuran, and methomyl include applications to
crop agricultural sites, residential sites, and urban sites. Registered 24(c) uses in Oregon include
carbofuran application to potatoes, nursery stock, sugar beets, and watermelons. Based on land
use patterns, we expect the highest exposure to these chemicals to occur in the Lewis River
basin, Clackamas River basin, and Hood River basin.
Mature LCR Fall-run Chinook salmon enter freshwater in August through October to spawn in
large river mainstems. After emergence, fry typically select off-channel habitats associated with
their natal rivers and streams. Juveniles eventually emigrate from freshwater, usually within six
months of hatching. LCR Spring-run Chinook salmon enter freshwater in March through June to
spawn in upstream tributaries. These fish generally emigrate from freshwater as yearlings. As
juveniles overwinter in shallow, freshwater habitats, they are likely to experience higher
exposure to pesticides, other contaminants, and elevated temperature. In northern rivers,
juveniles may rear in freshwater for two years or more. Given their long residence time in
shallow freshwater habitats, LCR Chinook salmon are vulnerable to high pesticide exposures.
Also, if adults and juveniles are within Willapa Bay during 24(c) carbaryl application to oyster
beds they are likely exposed to this compound and may likely experience additional mortalities.
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