A. Status of the Spectacled Eider - U.S. Fish and Wildlife Service

As can be seen in Figure 1-2, the posterior distributions from the three surveys differ quite
dramatically. We used data from the last 15 years for all three surveys to estimate a joint
posterior distribution (Figure 1-3). Because the surveys were rather disparate, the analysis
required eight million random selections of parameters to obtain the posterior distribution.
Although the posterior distribution is very broad it is still highly likely that the YKD
population has declined over the past 15 years.
Figure 1-3. Prior and posterior distributions for only the last 15 years of all three surveys.
The re-sampled 10,000 sets of values for the eight parameters represents thejoint posterior
distribution. We utilize this joint posterior distribution to perform a PVA that includes the
uncertainty in our data (the abundance index surveys) and the model (prior information on
variability in r). We sequentially used each set of parameter values as input parameters for a
stochastic population projection. Required input parameters are: N 0, r, and s~. Each
simulation began with N0 individuals. The initial number, N0, was drawn from either the 1995
estimated abundance distribution for the Coastal or the Ground survey with equal probability.
The simulation proceeded according to equation 1 (below), where r’ was drawn from a Normal
distribution (mean = r, variance = ~ Both the time to extinction (