KLEIBER and BAKER: INTERACTION BETWEEN NORTH PACIFIC ALBACORE FISHERIES 



20t Longline Catch 



15-. 



sz. 

 u 



to 

 u 



10-. 



5  



Effortx2 : 



Baitboat 



Longl ine 



U.S. 



Effort/2 : 



Baitboat 

 Longl ine 

 U.S 



25 



I 



35 



t - 



45 



105 115 



125 



Length (cm) 



Figure 5. — Annual albacore longline catch-at-size in numbers predicted by the model under nominal and experimental conditions. 



1970s. The reliability of this conclusion, of course, 

 depends on the reliability of our simulation 

 model, but in evaluating the behavior of the 

 model, we should remember that what is impor- 

 tant is the response of the model to experimental 

 manipulation not the exactitude of the nominal 

 behavior in comparison to real data. Of course, if 

 the nominal behavior is outlandish, the responses 

 to manipulation will be suspect. Therefore we 

 used the average year as a signpost to tune the 

 nominal results of the model into the range of 

 plausible behavior, but we did not insist on exact 

 duplication of the average year (itself an abstrac- 

 tion that never happened in reality). 



A case in point is the longline catch, which 

 under nominal conditions in the model is less (in 

 weight) than any of the real annual longline 

 catches for the years 1970-80. The average over 

 those years is 13.3 metric kilotons (kt) per year 

 whereas the nominal longline catch in the model 

 is 9.47 kt/year (Table 1). The discrepancy is ex- 



plained by the fact that the average size offish in 

 the model longline catch is less than the average 

 size in the real longline catch, because large fish 

 in the model migrate out of reach of the longline 

 fleet more than they should. We have not cor- 

 rected this problem because we are waiting for 

 further information from tagging studies to get 

 better estimates of migration coefficients. We ex- 

 pect the corrections to be quantitative refine- 

 ments of the existing values and not a qualitative 

 change in the current migration pattern in the 

 model. 



What is important in the current context is that 

 bias in the nominal results is bound to show up in 

 the experimental results as well. The migration 

 coefficients were the same in both control and 

 experimental situations in the model. Therefore, 

 refinements to the coefficients are not likely to 

 make much difference in the relative values in 

 Tables 2 and 3, particularly in the percentages. It 

 is pertinent that our conclusion of low interaction 



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