Biological Information 



Fisheries management has traditionally 

 been based on biological considerations. 

 Therefore biological data are more sophisti- 

 cated and research concepts are better under- 

 stood than those for economic or social infor- 

 mation, and biological research has been 

 funded at a high level by Federal and State 

 agencies concerned with fisheries manage- 

 ment. 



The principal biological data tool is stock 

 assessment,63 the study of marine fish popula- 

 tions in terms of their potential commercial 

 yield, as well as the limits of that yield. Stock 

 assessment attempts to develop an under- 

 standing of marine ecosystems and the effects 

 of man's activities upon them. The mecha- 

 nisms that drive marine ecosystems, as well as 

 those that drive fishing activities, if under- 

 stood and if properly applied, serve as one 

 means to predict the effects of future activities. 

 Therefore, stock assessments can and do con- 

 tribute to fisheries management decisions. 



Stock assessments seek to develop informa- 

 tion on what the maximum sustainable yield 

 (MSY) of a fishery is. That is, fisheries are 

 viewed as a renewable resource, dependent 

 upon: 



. the introduction of young fish into the 

 population (recruitment); 



. their rate of growth; 



» their natural mortality; 



• themortality caused by fishing activities. 



The management goal is to not remove 

 more from the population than can be 

 replaced, thus allowing maintenance on a 

 steady basis of an allowable surplus over and 

 above the parental stock necessary to produce 

 that surplus. The principle that catch should 

 not exceed the MSY has found nearly univer- 

 sal acceptance in the international fishing 

 community. 64 



Stock assessment has traditionally served 

 two purposes: provision of information and 

 data for the development of new fisheries, and 

 provision of information to maintain a stock 

 or to restore depleted fisheries. 



There exist a large number of uncertainties 

 with existing stock assessment science: 

 problems with the data generated and more 

 importantly, problems concerning the use of 

 that data. 65 of paramount importance is the 

 fact that offshore marine fisheries, particularly 

 ground fish (demersal species), constitute 

 populations that are nearly impossible to ob- 

 serve until harvested. As a result, assessment 

 must depend upon inference, statistical prob- 

 abilities, and the measures developed to un- 

 derstand the complicated and interrelated 

 marine environment. As such, assessments 

 depend upon the analysis of past information 

 and trends to predict future fisheries develop- 

 ments. 



Fishing activities have continually changed 

 as technologies have developed. These 

 changes force adjustments in past-data 

 analysis to reflect future realities. Further, as 

 fishing activities have varied, there are en- 

 vironmental fluctuations and trends that are 

 long-term in nature and are, as yet, poorly un- 

 derstood. This understanding is extremely 

 difficult when technological changes con- 

 tinually alter the data simultaneously. 



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