Y KE(l - E/r) (8.60) (using (8.56)). These results are shown graphically in Figure 8.9. The dashed curve is the plot of x against x, and its corJ1ponents, F(x) and Ex are shC1im separately. The yie1deffort (Y - E) curve, from Equation (8.60), is plotted in Figure 8.10. This shows that the maximum sustainable yield occurs when E = r/2. If effort is increased beyond this level, then the yield decreases smoothly until it reaches zero at E = r.