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

The Status of Listed Resources and Environmental Baseline sections indicate that dams and other
migration barriers, urbanization and channel modification, agricultural activities, introduced nonnative
predators, hatcheries, and large scale water management and diversions negatively affect
this DPS. Steelhead habitat has been highly degraded by reduced channel complexity, eroded
banks, increased water temperature, migration barriers restricting access to cooler head waters,
and decreased water quality from contaminants. Numerous NAWQA, CDPR, and other
assessments found high concentration of contaminants in both the San Joaquin and Sacramento
Rivers and their tributaries. In the San Joaquin Basin, seven pesticides exceeded EPA criteria for
aquatic life. These pesticides include diuron, trifluralin, azinphos-methyl, carbaryl, chlorpyrifos,
diazinon, and malathion. The combined impacts from these threats continue to affect the CCV
steelhead.
Approximately 27% of the land within the DPS is developed for cultivation of crops (Table 38).
High densities of crop farming occur throughout the San Joaquin Basin, in the Sacramento-San
Joaquin Delta, and along lower Sacramento River. Further, 9.2% of the DPS consists of urban
development. Based on the crop types, we expect carbaryl, carbofuran, and methomyl are
commonly applied in the Central Valley throughout the growing season. In urban and residential
areas, we expect carbaryl to be applied throughout the year. Monitoring in the San Joaquin basin
found 48 of 83 pesticides tested for. Seven pesticides (diuron, trifluralin, azinphos-methyl,
carbaryl, chlorpyrifos, diazinon, and malathion) exceeded criteria for the protection of aquatic
life. Pesticides detected in the Sacramento River included thiobencarb, carbofuran, molinate,
simazine, metolachlor, dacthal, chlorpyrifos, carbaryl, and diazinon. Carbofuran was most often
detected in agricultural sites while carbaryl was also found in all urban sites tested.
All of the steelhead populations within this DPS exhibit the winter-type life history, though
detailed information about the CCV steelhead life history is not available. Juvenile steelhead
remain in freshwater for one or more years before migrating downstream to enter the ocean. The
CCV steelhead use the lower Sacramento River and the Delta for rearing and as migration
corridor. Some may utilize tidal marshes, non-tidal freshwater marshes, and other shallow areas
in the Delta for rearing areas for short periods during outmigration to the ocean.
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