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

higher concentrations compared to the “all studies” plots. This is likely a reflection that when
individual study results are considered separately, the species with the greater number of EC50
study results is found at the lower end of the distribution.
Table 79. Carbaryl, carbofuran, and methomyl survival EC50 concentrations at 50 th , 10 th , and 5 th
percentiles from probability distribution plots.
Concentration of EC50 at each percentile (μg/L)
50% 10% 5%
All studies probability distribution plot
Carbaryl 45.23 2.29 0.98
Carbofuran 58.95 0.94 0.29
Methomyl 128.9 12.93 6.74
Species geometric means probability distribution plot
Carbaryl 69.53 4.33 1.97
Carbofuran 89.95 1.22 0.37
Methomyl 150.76 20.74 11.82
We selected the 10 th percentile from each of the pesticide plots to represent the survival EC50 for
salmonid prey. The associated 10 th percentile for carbaryl (4.33 μg/L), carbofuran (1.22 μg/L),
and methomyl ( 20.74 μg/L) was used as input for the population growth model exercises. The
10 th percentile is a reasonable selection because the data included in the meta-analysis were
limited to concentrations that caused mortality or immobilization within a short period of time
(1-4 days). A growing number of studies on a variety of insecticides have reported that
concentrations well below LC50s can cause delayed mortality or sublethal effects that may scale
up to affect aquatic invertebrate populations, especially in scenarios with multiple exposures
and/or other stressors. Evidence for ecologically significant sublethal or delayed effects to
aquatic invertebrates includes reduced growth rates (Schulz and Liess 2001; Forbes and Cold
2005), altered behavior (Johnson, Jepson et al. 2008), reduced emergence (Schulz and Liess
2001; Johnson, Jepson et al. 2008), reduced reproduction (Cold and Forbes 2004; Forbes and
Cold 2005), and reduced predator defenses (Sakamoto, Chang et al. 2006; Johnson, Jepson et al.
2008).
Additionally, the available toxicity data – and therefore the data included for these analyses– are
from studies using taxa hearty enough to survive laboratory conditions. Studies specifically
examining salmonid prey that are more difficult to rear in the laboratory have documented
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