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

occupy shoreline habitats of only a few centimeters in depth before moving further off-shore and
taking on a more pelagic existence. Coho salmon, Chinook salmon, and steelhead fry typically
select off-channel habitats associated with their natal rivers and streams. These species are most
likely to experience higher pesticide exposures given their utilization of shallow freshwater
habitats as juveniles for rearing. Coho salmon and steelhead have a greater preference for the
shallow habitats and rear in freshwater for more than a year.
Substantial data gaps in EPA's exposure characterization include exposure estimates associated
with product uses on many crops and particularly, on non-crop uses. The highest concentrations
detected in surface waters were those associated with applications to aquatic habitats. Those
types of applications although mentioned, were not evaluated in EPA’s BEs. Additionally,
exposure estimates for other chemical stressors including other ingredients in pesticide
formulations, other pesticide products authorized for co-application, adjuvants, degradates, and
metabolites are not available or are non-existent. Although NMFS is unable to comprehensively
quantify exposure to these chemical stressors, we are aware that exposure to these stressors is
likely. We assume these chemical stressors may pose additional risk to listed Pacific salmonids.
However, in order to ensure that EPA’s action is not likely to jeopardize listed species or destroy
or adversely modify critical habitat, NMFS analyzes exposure based on all stressors that could
result from all uses authorized by EPA’s action.
Response Analysis
In this section, we identify and evaluate toxicity information from the stressors of the action and
organize the information under assessment endpoints (Figure 37). The endpoints target potential
effects from the stressors of the action to individual salmonids and their supporting habitats. The
assessment endpoints represent biological attributes that, when adversely affected, lead to
reduced fitness of individual salmonids or degrade PCEs (e.g., prey abundance and water
quality). We constructed a visual conceptual model to guide development of risk hypotheses and
assessment endpoints to highlight potential uncertainties uncovered by our analysis of the
available information. We begin the response analysis by describing the toxic mode and
mechanism of action of carabaryl, carbofuran, and methomyl. Next we summarize the toxicity
data presented in the three BEs and organize the information to applicable assessment endpoints
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