37


sustainable yield is imposed on the relationship between catch and

effort. Very little attention has been given to equations of this type.

The most notable exception is a paper by Bell et al. (1973) wherein they

addressed the question of constant versus decreasing returns in an

essentially non-equilibrium framework. Within the framework of bio-

economics it may seem objectionable to consider analyzing fishery pro-

duction without implicitly incorporating biological concepts in the form

of population dynamics. A closer examination of non-equilibrium yield

functions may serve to lessen these objections.

 One of the primary reasons for analyzing fishery production is to

 develop analytic models which can be used in studying the effects of

 various management alternatives. Non-equilibrium yield functions are

 very amenable to such types of analysis for two reasons. First, this

 class of functions provides a much wider range in the choice of func-

 tional relationships between catch and effort. This is especially

 significant in that equilibrium yield functions generally treat fishing

 effort as a single variable or composite measure. Non-equilibrium

 models, however, can be specified in several variables which serve to

 decompose effort into components which greatly enhance the analytic

 ability of the model with respect to management questions. Secondly,

 with the appropriate stochastic incorporation of unobservable population

 effects, non-equilibrium yield functions can be used to derive equilib-

 rium yield relationships.7 Unless otherwise stated, all yield (catch)

 equations in the ensuing analysis will be non-equilibrium in nature.


 7The notion of derived equilibrium yield equations is developed in
 the following chapters.