latent resources capable of significant increases in 

 output, others that are already being exploited at 

 or beyond levels that maximize their contribution 

 to the U.S. economy. The same situation prevails 

 in all resource-oriented industries. In forest prod- 

 ucts, for example, there are serious adjustment 

 problems resulting from cutting in excess of 

 annual growth rates in some areas, while other less 

 accessible forest areas, remain hghtly harvested or 

 completely untouched. It is necessary to impose 

 strict controls on the production of oil in some 

 areas while pursuing vigorously new sources, both 

 onshore and offshore. 



A rational Federal fishery program must deal 

 simultaneously with regulation of some species to 

 prevent depletion or even destruction, while pro- 

 viding all possible incentives for expansion of 

 catches where biological limits have not been 

 reached. It is of crucial importance, however, that 

 all fishery management agencies and programs be 

 cognizant of this dual responsibility. All too 

 frequently regulatory programs have had the ef- 

 fect of slowing down or preventing the kinds of 

 technological development required to expand 

 operations on species not fully utilized. 



Brief reference was made in the preceding 

 section to the division of responsibility between 

 Federal and State governments with respect to 

 management of fishery resources, including both 

 regulation programs and enhancement and propa- 

 gation programs. There is great difficulty imposed 

 on any National concept of fishery management 

 under the present division of authority among 

 Federal and State agencies, and the need for the 

 kind of reorganization discussed in Section VIII 

 becomes apparent from the following discussion. 



A. Biological Determinants of Physical Yields 



The commercial fisheries of the world rest on 

 the productive capacity of a series of closely 

 interdependent organic populations. Like a forest, 

 perhaps the most similar type of useful Uving 

 resource, a fish population exists in an enormously 

 complex environment. It is impossible, however, 

 to observe directly the size and composition of a 

 specific fish population, nor can environmental 

 conditions be controlled sufficiently to isolate the 

 impact of specific changes known to affect it. 

 Properly conducted, exploratory fishing can pro- 

 vide useful preliminary estimates of standing 



stocks and yield potentials. More refined estimates 

 of the production possibilities from a given fishery 

 resource cannot really be made until a well 

 developed commercial fishery is operating on it. 



The key variables determining production pos- 

 sibiUties from a fish population can be grouped 

 under three headings: rate of entry into the 

 "fishable" age (recruitment), growth rates of in- 

 dividual fish, and natural mortaUty (from disease, 

 old age, and non-human predators). In the absence 

 of human intervention, a marine population tends 

 toward a maximum aggregate weight, or biomass, 

 at which net increments to stock from recruitment 

 and growth are exactly offset by decrements from 

 natural mortality. Thus, at zero and at maximum 

 population levels the instantaneous rate of change 

 in the weight of the fishery population is zero. At 

 intermediate levels, the aggregate weight of the 

 stock, in the absence of other disturbances, will 

 tend to rise toward its maximum value, and the 

 instantaneous rate of change in weight will be 

 positive. It must be recognized, of course, that 

 these long run equihbrating tendencies may be 

 obscured by changes in the complex environments 

 of the sea. 



Assuming for the moment that recruitment and 

 growth rates are independent of population size, 

 these relationships can be translated into a simple 

 physical production function. As fishing effort on 

 an undisturbed stock (expressed in terms of 

 standard units) is increased from zero level, sus- 

 tainable yield— that is, the catch equal to the 

 instantaneous rate of change in biomass in the 

 absence of fishing by man— increases at a de- 

 creasing rate, while the number and average size of 

 fish will decline continuously. If the selectivity of 

 the gear with respect to fish of different sizes is 

 held constant, the sustainable yield will peak at 

 some level of fishing effort. Further increases in 

 fishing effort will produce an absolute decline in 

 sustained physical yield. Assuming a recruitment 

 rate independent of population, fishing by man 

 wiU yield a larger net physical product as long as 

 the marginal reduction in weight losses from 

 natural mortahty is greater than the marginal 

 weight loss resulting from capture of individual 

 fish before they achieve maximum weight. Not all 

 fisheries will show such a peak, however; given 

 constant recruitment, the age at entry into the 

 fishery, the individual fish growth function, and 

 mortality rates will determine whether or not the 



VII-62 



