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

support one or more lifestages. For this opinion, the primary PCEs potentially affected are prey
availability and water quality degradation in spawning and rearing areas, freshwater migratory
corridors, and nearshore and estuarine areas.
The effects of the proposed action on prey and water quality PCEs are addressed below by
weighing the available evidence either supporting or refuting the critical habitat-related risk
hypotheses. NMFS reviewed and presented the toxicological information available for habitat
assessment endpoints within the Response Analysis section. Included are the PCEs prey
availability and water quality. If these PCEs are likely impacted by the stressors of the action,
we address the potential for reductions to the associated conservation value of the designated
critical habitat in the Effects of the Proposed Action to Designated Critical Habitat Section.
Critical Habitat Risk Hypotheses based on potential effects to PCEs:
Risk Hypothesis 1. Exposure to the stressors of the action is sufficient to reduce
abundances of aquatic prey items of salmonids.
We evaluated two lines of evidence to determine whether this hypothesis is supported by the
available information. The first is whether data support the occurrence of adverse effects to
salmonid prey items from the stressors of the action. The second is whether reductions in
abundances of salmonid prey items occur in areas of documented exposure to the stressors of the
action. We found overwhelming evidence in support of the first line of evidence. The stressors
of the action are expected to kill large numbers and types of aquatic species that serve as prey to
salmonids, especially when carbaryl, carbofuran, and methomyl are present together and/or cooccur
with other insecticides. The concentrations we summarized indicate that alone each of the
insecticides can also kill prey at expected environmental concentrations.
The IBI and other metrics of aquatic community health were reviewed to evaluate the second
line of evidence. In areas of intensive agriculture, where we expect use of the stressors of the
action, biological integrity is often significantly reduced (Cuffney et al 1997). Many of the
preferred salmonid prey items are present only in low numbers or absent altogether in these
areas. We see similar depauperate communities in urban areas. We recognize many other
limiting factors contribute to poor condition of these aquatic communities. However, these
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