FISHERY BULLETIN: VOL. 85, NO. 4 



Ba i tboa t Catch 



Effortx2 : 



. . Baitboat 



Longl ine 



U.S. 



Effort/2 : 



Ba itboat 



Longl ine 



U.S. 



115 



125 



Length (cm) 



Figure 4. — Annual albacore baitboat catch-at-size in numbers predicted by the model under nominal and experimental conditions. 



Table 2. — Interaction matrix for annual albacore catch in numbers. 

 The values given are the differences between the catch under 

 altered effort and the nominal catch (percent of nominal catch in 

 parentheses). 



effect 4> 



A catch: number y 106 (%) 



Table 3. — Interaction matrix for annual albacore catch in weight. 

 The values given are the differences between the catch under 

 altered effort and the nominal catch (percent of nominal catch in 

 parentheses). 



effect => 



A catch: kt (%) 



overall exploitation rate by repeating the whole 

 analysis at higher exploitation rates, starting 

 with the cohort analysis, correcting catchabilities 

 to give a new set of nominal results, and finally 

 measuring the most sensitive interaction, the ef- 

 fect of doubled baitboat effort on the longline 

 catch (Fig. 7). The degree of interaction is not 

 affected very much when the exploitation rate is 



below 10%, but it rises quickly at higher exploita- 

 tion rates. 



DISCUSSION 



Our results support the notion that fishery in- 

 teraction is not of great consequence, at least for 

 the North Pacific albacore fisheries typical of the 



708 



