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

Species Risk Hypotheses
We construct risk hypotheses by identifying biological requirements or assessment
endpoints (Table 4) for listed resources in the action area. We designate assessment
endpoints as those biological properties of species and their habitat essential for
successful completion of a species life cycle. We integrate the listed resources
information with what is known about the stressors of the action, including their physical
properties, use, presence in aquatic habitats, and their toxicity. We then evaluate how
listed salmonids and their habitat are potentially affected by the stressors of the action
and integrate this information with exposure information to develop risk hypotheses.
Below are the risk hypotheses (written as affirmative statements) we evaluate in the
Effects of the Proposed Action section:
1. Exposure to carbaryl, carbofuran, and methomyl is sufficient to:
a. Kill salmonids from direct, acute exposure;
b. Reduce salmonid survival through impacts to growth;
c. Reduce salmonid growth through impacts on the availability and quantity
of salmonid prey;
d. Impair swimming which leads to reduced growth (via reductions in
feeding), delayed and interrupted migration patterns, survival (via reduced
predator avoidance), and reproduction (reduced spawning success); and
e. Reduce olfactory-mediated behaviors resulting in consequences to
survival, migration, and reproduction.
2. Exposure to mixtures of carbaryl, carbofuran, and methomyl can act in
combination to increase adverse effects to salmonids and salmonid habitat.
3. Exposure to other stressors of the action including degradates, adjuvants, tank
mixtures, and other active and other ingredients in pesticide products containing
carbaryl, carbofuran, and methomyl cause adverse effects to salmonids and their
habitat.
4. Exposure to other pesticides present in the action area can act in combination with
carbaryl, carbofuran, and methomyl to increase effects to salmonids and their
habitat.
5. Exposure to elevated temperatures can enhance the toxicity of the stressors of the
action.
We discuss an example of one risk hypothesis to show the relationship between
assessment endpoints and measures with species responses. In risk hypothesis 1 (d),
aquatic exposure to carbaryl, carbofuran, and methomyl can impair a salmonid’s nervous
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