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 impaired stream flows and barriers to fish passage in tributaries from
hydroelectric dams. During the 1960s and 1970s, approximately 80% of the ESU’s historic
habitat was eliminated or severely degraded by the construction of the Hells Canyon complex
and the lower Snake River dams. Additionally, degraded freshwater habitats in the estuary,
mainstem, and tributaries from development and land use activities negatively affect this ESU.
Agricultural activities, urban communities, and industries are concentrated along the Snake River
and near the mouths of major tributary valleys. Thus, stream water quality and biological
communities in the downstream portion of the upper Snake River basin are degraded. The
combined impacts from these multiple threats continue to affect SR Fall-run Chinook salmon.
Registered uses of carbaryl, carbofuran, and methomyl include applications to crop agricultural
sites, residential sites, and urban sites. Registered 24(c) uses within this ESU include carbofuran
application to potatoes and spinach grown for seed in Washington. The remaining spawning and
rearing area of the SR Fall-run Chinook salmon is potentially a high-use area for these
chemicals, as it is adjacent to agricultural and residential areas. About 14% of the land has been
developed. Dryland agriculture occurs in the lower Clearwater Basin, with crops including
wheat, peas, and lentils. Alfalfa, hay, and grasses are also grown in the lower Clearwater as well
as the lower Salmon River basin. Thus, ESU exposure to these pesticides is likely. Adults
within Willapa Bay during 24(c) carbaryl application to oyster beds are likely exposed to this
compound and may experience additional mortalities.
Adult SR Fall-run Chinook salmon enter the Columbia River in July and August. Spawning
occurs from October through November above Lower Granite Dam in the mainstem Snake River
and in the lower reaches of the larger tributaries, such as the Salmon and Clearwater Rivers. Fry
emerge from redds beginning in March or April, then rear for two months or more in the sandy
littoral zone along the river margin. Juveniles begin migration in June along the edges of rivers,
where they are at risk of exposure to higher concentrations of pesticides from drift and runoff.
Their duration in shallow freshwater habitats increases their chances of higher exposure to
pesticides, contaminants, and elevated temperature. Most fish exhibit an ocean-type life cycle,
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