ABSTRACT
The results of the 500 simulations of each 50-year population trajectory were summarized by four plots for each species and pool (e.g., sauger in Robert Byrd pool, Figs. 3 and 4). The first and second plots show results of simulations for the population under the influence of the power plants and the results with the power plant effects removed (i.e., no fish lost via entrainment or impingement or the nopower-plant-effects model). In these plots, the broad, solid line shows the mean of the 500 simulations for each of the 50 years. The dashed lines show the 5th and 95th percentiles of the 500 simulations for each year. The narrow, solid lines show the minimum and maximum of the simulated populations for each year. The third plot (Fig. 4) is an overlay of the first two plots and illustrates how the population is predicted to respond if no fish were lost via impingement or entrainment. In these plots, the broad, dashed line is the estimate of the mean population if entrainment and impingement were eliminated (no-power-plants model). The broad, solid line is the estimated population under current conditions with the power plants operating and fish being lost due to impingement and entrainment. If the solid and dashed, broad lines follow a similar path (e.g., bluegill in Pike Island pool, Fig. 5), then no population level impacts would be predicted. However, if these two lines follow noticeably different trajectories (e.g., freshwater drum in Robert Byrd pool, Fig. 6), then impacts to that species in that pool may be occurring. The narrow, dashed line is the 5th percentile of the no-power-plants model and the narrow, solid line is the 5th percentile for the power plant model. To help with the interpretation of these boundaries, a fourth plot was developed that illustrates the frequency with which the simulations fall below the 5th percentile for more than a specified number of years. For example, for sauger in the Robert Byrd pool (Fig. 4), it can be seen that the probability of falling below the 5th percentile for at least one of the 50 years is about 0.55, which is relatively high; the probability of falling below the 5th percentile for at least 10 of the 50 years is about 0.06, which is a fairly rare event; and the probability of falling below the 5th percentile for 25 of the 50 years is essentially zero. The average change for each species and pool that would be expected if power plant entrainment and impingement could be removed is summarized in Table 3. This percent was calculated by finding the geometric mean of the abundance values from the 500 simulations for each year for both the power-plant and no-powerplant simulations. The average expected change for the 50 years is computed from these annual means. The change is calculated by the formula
percent change = 10(mn(nopp) - mn(pp))*100 − 100 (4)
where mn(nopp) is the mean of logarithms of total population of the no power plant simulations and mn(pp) is the mean of logarithms of total population of the power plant simulations. The projected changes range from a 3% decrease for white bass in Robert
FIGURE 3A
FIGURE 3B
FIGURE 3. Simulation results for sauger population in the Robert Byrd pool with and without the influence of power station entrainment and impingement.
