54 



Fishery Bulletin 105(1) 



B 



Figure 3 



Hotspots of bigeye tuna iThunnus obesus) catches in relation to skipjack tuna 

 {Katsuwonus pelamis} catches by seasonal quarter and 5°x5'" region for 1995-2002 

 as measured by our hotspot index (Equations 1-3). Plots A-D represent quarters 

 1-4. Shades are used for different percentiles of the index, and darker regions 

 indicate areas of higher bycatch rates. The black regions represent those time 

 and area strata for which the hotspot index was in the top 20%. 



Results 



Hotspots 



The hotspots were not evenly spread over the year; 

 the third seasonal quarter contained more 5°x5° hot- 

 spots (24) than the other quarters (15-18 each) (Fig. 3). 

 During quarters 1 and 4, most of the hotspots were 



located between 5°N and 10°S, whereas during quarters 

 2 and 3, the hotspots extended south to 15°S. Over all 

 time-area strata, 90% of the hotspots were west of 90°W 

 and east of 135°W, and over 95% were between 5°N and 

 15°S — indicating that the hotspots are found within a 

 fairly restricted area. 



When we compared the hotspots to the practical clo- 

 sure, 75% of the hotspots were found within the prac- 



