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

insecticides and their formulations may be responsible for a substantial portion. In fact, several
studies have shown toxicity to salmonid prey items from field collected waters and sediment due
to pesticide residues (Cuffney, Meador et al. 1997; Hall, Killen et al. 2006).
We therefore expect that spawning, rearing, and migratory areas will be affected by the stressors
of the action resulting in reduced abundances of aquatic prey items. The magnitude in reduction
of prey is difficult to ascertain, however where designated critical habitats overlap with high
potential use areas such as agricultural or urban dominated flood plains, we expect pronounced
reductions. These areas support fry and juvenile growth and development which are predicated
on an abundant and diverse source of prey. Reductions in prey availability may affect the
conservation value and the ability of the habitat features to support salmonids. In summary, the
available information shows prey items of ESA-listed salmonids are affected by the stressors of
the action to an extent warranting an analysis of whether the conservation value of designated
critical habitat is negatively affected.
Risk hypothesis 2. Exposure to the stressors of the action is sufficient to degrade water
quality in designated critical habitat.
We addressed this hypothesis by comparing exposure concentrations to toxicity data. The results
of the comparison indicate that expected concentrations from the proposed action trigger adverse
effect levels for salmonids and their prey (see Exposure Analysis and Response Analysis
sections). Based on pesticide uses described in the Description of the Action section coupled
with expected concentrations presented in the Exposure Analysis section (i.e., concentrations
derived from surface water monitoring data, EPA and NMFS modeling estimates), we expect
these concentrations to be present in designated critical habitat and therefore to degrade water
quality. In many of the watersheds containing designated critical habitats, water quality is
identified as a major limiting factor to salmonid production. The proposed action is likely to
further degrade water quality in spawning, rearing, and migratory areas. Collectively, this
information supports the conclusion that designated critical habitats are likely degraded
throughout the four states and further analysis is warranted to determine the potential to reduce
the conservation value of designated critical habitats.
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