The Schaefer (1957) sustainable yield function given in equation

(9) is restated below as


 c = aE (b E) (C-l)


where c denotes catch and E is defined as fishing effort and a and b are

constants. Maximum sustainable yield corresponds to the maximum of

equation (C-1). The effort level corresponding to maximum sustainable

yield is obtained by solving the first order condition for the maximum

of equation (C-1) for E. Setting


 dC = ab 2aE (C-2)
 dE


equal to zero and solving for E, yields

 b
 E = (C-3)


where E denotes the level of fishing effort which produces maximum

sustainable yield.

 To obtain the effort level corresponding to maximum economic yield,

an industry profit function is required. This function, within the

context of the Schaefer model, is given by

 n = Pa E(b E) rE (C-4)


where i denotes profit, P is the constant product price, r is the unit

cost of effort, assumed constant, and all other terms are defined as

above. The effort level which results in maximum economic yield is

obtained by solving the first order condition for the maximum of

equation (C-4) in terms of E. By setting