40


the open access result of total cost equals total revenue holds. Thus,

it can be seen that relaxation of the constant price assumption does

indeed confuse and complicate many of the theoretical results derived by

using equilibrium yield functions.

 Utilizing non-equilibrium yield functions can avoid some of these

complications. Let the yield function for a fishery be defined by


 C = f(X1, ..., Xn) (23)


where C denotes output and the X. corresponds to n inputs. It is
 1
further assumed that f(X1, ..., X ) is such that


 > 0 i = 1 ..., n (23a)
 aXi

 i
 2
 < 0 i = 1, ..., n (23b)
 aX


Equations (23a) and (23b) merely assert that the marginal product func-

tion is everywhere positive and declining. The price of output is now

defined to be a declining function of catch


 P = P(C) (24)

 dP
where d < 0. Finally, the cost equation is defined by
 dC

 n
 K = r. X. (25a)
 i=1 l 1


where the input prices, ri, are assumed constant. From equation (25a),

the marginal cost of Xi is then given by