INTRODUCTION 



This working paper was prepared for the Office of Technology Assessment 

 as a part of its study of the background, methods and complexities of stock 

 assessment and the role of such assessments in implementing the Fisheries Con- 

 servation and Management Act of 1976. 



Passage of that law extended United States fisheries jurisdiction to 200 

 miles off the coast. Such action put one-fifth of the worldwide offshore groundfish 

 resources under national management control. Management jurisdiction was extended 

 in the spring of 1976, with initial management plans for selected species to enter 

 into effect on March 1, 1977. Extension became necessary when it was realized 

 that international management of offshore fishery resources had failed; the 

 common-property nature of the fisheries prevented any individual or nation from 

 assuming management control. 



Stock assessment of fishery resources developed over time in response to 

 the felt need that measures were necessary to predict species abundance and yield 

 potentials according to different chosen priorities. Initially concentrating on 

 single species, assessments sought to determine the abundance of year-classes, 

 recruitment of individuals into the stock, the natural mortality of the stock, and 

 the fishing mortality to be expected from man's harvesting activities. 



Determination of stock abundance and size was accomplished through use of 

 survey tows, size and age composition of individual fish, tagging experiments, 

 and development of sophisticated models that were based on stratified random 

 sampling techniques. Such sampling partly overcame the problem that it was 

 impossible to observe fish populations directly. 



As distant-water fleets developed during the 1950s and 1960s, assessments 

 concentrated on providing information for the development of new fisheries in 

 frontier areas. Such information required abundance 



