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productive uses. Thus, when equations (19a) and (19b) are simultaneously

zero, an open access bioeconomic equilibrium is said to exist.

 An example of such a system of equations is pictured in Figure 6.

Points above the I(X, V) = 0 curve correspond to points where industry

profits are negative while the converse holds for points below the

function.




 I (X, V) = 0




 ( A




 F(X, V) = 0

 Resource stock (X)

 Figure 6. Phase diagram for equilibria between vessels and
 resource stock in an open access fishery



 Similarly, points above the F(X, V) = 0 curve correspond to harvest

rates in excess of sustainable yield. The arrows in the diagram cor-

respond to the direction of change in vessels and resource stock.

Immediately obvious is the fact that there are three potential equi-

librium positions (points A, B and C). Only points A and C represent

stable solutions, however. The instability of point B can be seen by

examination. Any displacement from this point would result in a new

equilibrium being established at point A or C.