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

distribution, are expected to die based on all three exposure estimate ranges, with the highest
rates of mortality based on EPA estimates and NMFS’ off-channel habitat estimates. The
magnitude of reduction in prey abundance will depend on which taxa are present in the exposed
water body and the actual concentrations and exposure durations. If reductions in prey
abundance, especially of the smaller organisms, coincide with fry feeding for the first time
following yolk sac absorption, starvation is likely. We discuss this in greater detail in the risk
hypotheses below. The lower value of the fish reproduction endpoint, 31 µg/L, overlapped with
both EPA’s and NMFS’ off-channel habitat estimates, and the highest value in the monitoring
data was greater. A notable data gap is the absence of information on methomyl’s toxicity to
olfactory-mediated behaviors. Although we found no studies that evaluated swimming, we
expect swimming impairment at concentrations less than LC50s because swimming is impaired
with other AChE inhibitors and AChE inhibition correlates to impaired swimming (Little and
Finger 1990; Little, Archeski et al. 1990).
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