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

natural cover such as submerged and overhanging large wood, aquatic vegetation, large
rocks and boulders, and side channels; and
6. offshore marine areas with water quality conditions and forage, including aquatic
invertebrates and fishes, supporting growth and maturation.
At the time that each habitat area was designated as critical habitat, that area contained one or
more PCEs within the acceptable range of values required to support the biological processes for
which the species use that habitat. We identified PCEs of prey availability and water quality in
freshwater spawning sites, freshwater rearing sites, migratory corridors, and estuarine and
nearshore marine areas as susceptible to the effects of the proposed action. We evaluated
whether prey availability and water quality are likely affected by the proposed action and
formulated risk hypotheses for these PCEs. We relied upon pesticide use information (see the
Description of the Action section), surface water monitoring data, EPA modeling estimates, and
NMFS modeling estimates (see Exposure Analysis section) to determine likely aquatic
concentrations. Based on our analysis within the Effects of the Proposed Action section, the
proposed action will reduce prey availability and degrade water quality within freshwater
spawning habitat, freshwater rearing habitat, and migration corridors.
Direct exposure to carbaryl, carbofuran, and methomyl and the other chemical stressors of the
action within freshwater will have an effect on Pacific salmonid critical habitat that overlaps with
intense agricultural and residential/urban land uses. The Environmental Baseline discusses the
extent of anthropogenic alteration of salmonid habitat within the action area. As established in
Effects of the Action to Listed Species Section, agricultural, urban, and residential areas overlap
with salmonids’ geographic range to differing degrees between ESUs/DPSs. As noted in the
Effects of the Proposed Action section, pesticides most often occur in the aquatic environment as
mixtures. Carbaryl, carbofuran, and methomyl are found in environmental mixtures. Based on
evidence of additive and synergistic effects of these compounds, we expect mortality of large
numbers and types of aquatic insects, which are prey items for salmon. A reduction in salmonid
prey abundance poses subsequent impacts on the overall growth of salmonid juveniles,
especially during their first year of survival.
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