done by Rich would serve as but one component 

 in the simulator described by Crutchfield, 

 albeit possibly the dominant component. 



Bell, Carlson, and Waugh focus on the issue 

 of diminishing returns in fisheries, relaxing a 

 strong assumption of fixed proportionality 

 utilized by most writers in the existing literature. 



The motivation for this exercise is the ap- 

 preciation that we are rapidly approaching total 

 utilization of the world's fish resources. As this 

 point is approached, demand pressures and 

 considerations of maximum efficiency dictate 

 the need to make maximum use of these 

 resources consistent with any overriding con- 

 sei-vation objectives. The work done by these 

 authors, though preliminary, suggests that 

 some degree of diminishing returns can be 

 identified for the fisheries studied: Chesapeake 

 Bay menhaden, Atlantic and Gulf blue crab, 

 Atlantic longline tuna, Bering Sea king crab, 

 and Cape Flattery sablefish. 



As with the other five papers in this section, 

 this paper modifies existing biological functions. 

 The modified logistic introduced here is the 

 author's candidate for a "better" function, 

 based primarily on the inclusion of diminishing 

 returns in the logistic specifications. As with 

 the other contributions this paper suggests 

 an area meriting further discussion in the near 

 future, with our best use of marine food re- 

 sources being the stake. 



Thompson continues the parade of alternative 

 functions with his concern being the absence 

 of a proper dynamic component within the 

 prevalent fisheries models. To correct this 

 error he proposes the marriage of the Schaefer 

 model and the Thompson-George (TG) produc- 

 tion-investment model. He also suggests some 

 alterations in the Schaefer model. 



The TG model replicates the sequence of 

 investment-production decisions which are in- 

 volved in the operation of the individual fishing 

 firm (vessel). Pertinent stocks and flows are 

 specified with elaborate preconditions for entry, 

 though there are no provisions for entry within 

 the decision period, an interesting trait in light 

 of the Johnson fixed asset theory as referred 

 to by Stevens and Mattox subsequently. By 

 adjoining this model to the Schaefer biological 

 fluctuation we have a bioeconomic model which 

 is uniquely micro in character; the dynamics of 

 change in the fishery stock (and hence fishing 



success) will be reflected in the investment 

 decision of the sole owner as the limiting case, 

 and vice versa. 



This method avoids the critical use of static 

 methods prevalent in economic literature. In- 

 herently, the adjustment mechanism in the 

 individual owner also facilitates the modification 

 of the Schaefer function to incorporate decreas- 

 ing returns to effort, as discussed by Bell, 

 Carlson, and Waugh and by Rich and increasing 

 returns to scale. Relaxation of the sole owner 

 condition further amplifies the critical nature 

 of these alterations and within the confines of 

 standard economic assumptions reaffirms the 

 desirability of limiting entry and suggests an 

 additional method of measuring the critical 

 management variables. 



The final author in this section addresses 

 the problem of multiple species fisheries — or 

 combination vessels. In this regard three issues 

 are of prime importance to Adam. The first of 

 these relates to the existence of yield curves for 

 fisheries. Adam views most of these curves as 

 average curves, pointing out that for many 

 fisheries this average curve will be bounded by 

 upper and lower curves which are usually the 

 result of substantial fluctuations in either 

 effort and/or recruitment. The average curve 

 is essentially a product of a stable fishery where- 

 as the boundary curves are the result of a 

 rapidly growing fishery. In his opinion we do 

 not move along the average curve as a fishery 

 rapidly develops. We move from one curve to 

 another, somewhat erratically as the fishery 

 develops. He looks to the economist, via a 

 function akin to Carlson, where effort is value- 

 dependent, to indicate what effort will be in 

 subsequent years, as the fisherman's response 

 to his monetary success is one of the few 

 reliable variables which can be presented to a 

 biologist in such a dynamic situation. 



His second point extends this argument to 

 multiple species. If a vessel has the capability 

 to adjust his harvesting pattern based upon 

 conditions in the fishery or the market, this 

 would preclude estimation based solely on 

 biological factors. It suggests that many of 

 these calculations must be made instantaneously, 

 at that time each year when a fishery is being 

 initiated. It suggests also that this must be 

 done for several fisheries simultaneously if 

 those fisheries are interrelated. For the North- 



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