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

the n x n square matrix (A) by assigning each age a number (1 through n) and each transition
from age i to age j becomes the element aij of matrix A (i = row, j = column) and represent the
proportion of the individuals in each age passing to the next age as a result of survival. The
reproductive element (a1j) gives the number of offspring that hatch per individual in the
contributing age, j. The reproductive element value incorporates the proportion of females in
each age, the proportion of females in the age that are sexually mature, fecundity, fertilization
success, and hatch success.
In order to understand the relative impacts of a short-term exposure of a single pesticide on
exposed vs. unexposed fish, we used parameters for an idealized control population that exhibits
an increasing population growth rate. All characteristics exhibit density independent dynamics.
The models assume closed systems, allowing no migration impact on population size. No
stochastic impacts are included beyond natural variability as represented by selecting parameter
values from a normal distribution about a mean each model iteration (year). Ocean conditions,
freshwater habitat, fishing pressure, and marine resource availability were assumed constant and
density independent.
In the model an individual fish experiences an exposure once as a sub-yearling (during its first
spring) and never again. The pesticide exposure is assumed to occur annually. All sub-yearlings
within a given population are assumed to be exposed to the pesticide. No other age classes
experience the exposure. The model integrates this as every brood class being exposed as subyearlings
and thus the vital demographic rates of the transition matrix are continually impacted in
the same manner. Regardless of the level of AChE inhibition due to the direct exposure, only the
sublethal effects are incorporated in the models at this time.
The model recalculates first-year survival for each run using a size-dependent survival value
selected from a normal distribution with the mean and standard deviation produced by Equation
S. Population model output consists of the percent change in lambda from the unexposed control
populations derived from the mean of two thousand calculations of both the unexposed control
population and the pesticide exposed population. Change in lambda, representing alterations to
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