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Fishing effort must be measured, as well. How effort is expressed 

 in international fisheries depends upon chosen catchability coefficients, 

 which apply to all of the vessels in the fishery. Again, this tends to 

 be reported information. There often are doubts about the number of 

 vessels in a fishery--highly mobile trawlers can move rapidly and must 

 be reported to be counted. Such coefficients do not respect the skill 

 of the skipper, which can be critical, particularly with regard to extremely 

 limited and hard-to-find stocks. 



Both catch and effort calculations depend upon the monitoring of 

 individual harvesting units, a task that could be determined with certainty 

 only if every vessel were observed. Remote sensing or random searches as 

 currently practiced are distorted by weather conditions (fog, for example, 

 prevents observation overflights), limits on capability in terms of budget, 

 and nighttime fishing. 



Fishing effort calculations must make assumptions about the type of 



gear used, probable return in terms of weight, and relationship between the 



standard unit and likely harvest. As fleets have increased and return 

 has dropped, there have been tremendous technological developments 



to improve the efficiency of the effort. Use of radar, loran, fish- 

 finders, and information from survey tows has in each instance allowed 

 the skipper to increasingly refine his fishing effort. As fish grow 

 scarce, this is only logical, at least while allocation problems remain 

 unsolved. 



These developments have, in nearly all cases, forced readjustments 

 of effort coefficients and have consequently distorted the validity 

 of the historical data. Particularly within the past decade, fishing 



