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

distributed survival and reproductive rates and model output consists of the percent change in
lambda from unexposed control populations derived from the mean of 1,000 calculations of both
the unexposed control population and the pesticide exposed population. The percent change in
lambda is considered different from control when the difference is greater than the percent of one
standard deviation from the control lambda.
Results
Sensitivity Analysis
A sensitivity analysis conducted on the organismal model revealed that changes in the control
somatic growth rate had the greatest influence on the final weights (Table 1). While this
parameter value was experimentally derived for another species (sockeye salmon; Brett et al.
1969), this value was adapted for each model species and is within the variability reported in the
literature for other salmonids (reviewed in Weatherley and Gill 1995). Other parameters related
to the daily growth rate calculation, including the growth to ration slope (Mgr) and the control
ration produced strong sensitivity values. Initial weight, the prey recovery rate and the prey floor
also strongly influenced the final weight values (Table 1). Large changes (0.5 to 2X) in the other
key parameters produced proportionate changes in final weight.
The sensitivity analysis of all four of the control population matrices predicted the greatest
changes in population growth rate (λ) result from changes in first-year survival. Parameter
values and their corresponding sensitivity values are listed in Table 4. The elasticity values for
the transition matrices also corresponded to the driving influence of first-year survival, with
contributions to lambda of 0.33 for coho, 0.29 for ocean-type Chinook salmon, 0.25 for streamtype
Chinook salmon, and 0.24 for sockeye.
Model Output
Organismal and population model outputs for all scenarios are shown in Tables 74-78 and were
summarized in Figures 44-47 in the main text of the Opinion. As expected, greater changes in
population growth resulted from longer exposures to the pesticides. The factors driving the level
of change in lambda were the Prey Drift and relative AChE Activity parameters determined by
the toxicity values for each pesticide (Table 3). The low Prey Abundance EC50 values drive the
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