Harley and Suter: Potential use of time-area closures to reduce the catches of Thunnus obesus in eastern Pacific Ocean 



55 



Quarter 3 



D 



Quarter 4 



Figure 3 (continued) 



tical closure area. Of the remaining 25'7f of hotspots, 

 most were west of 120°W. 



Time-area simulations 



Over all years and quarters, the predicted decrease in 

 bigeye tuna catches associated with the hotspot closure 

 ranged from 2.8% to 23.7%, whereas the change in 

 skipjack tuna catches ranged from a 0.9% increase to 

 a 14.1% reduction (Fig. 4). The greatest reductions in 

 bigeye tuna catch were associated with second- and 

 third-quarter closures (mean reduction = 14.6%). The 

 mean reductions in skipjack tuna catches did not vary 



much across quarters (means ranged from 2.8% to 3.7%). 

 For several years, there was little or no predicted reduc- 

 tion in skipjack tuna catch associated with a hotspot 

 closure. Based on the median of the ratios, the greatest 

 contrast between bigeye and skipjack tuna catch reduc- 

 tions was associated with a third quarter closure; the 

 average percentage reduction in bigeye tuna catch was 

 14.6%, versus 2.8% for skipjack tuna. The performance 

 of second-quarter closures was similar to that of third- 

 quarter closures, but the former was much more variable 

 across years. 



The performance of the practical closure was generally 

 similar to that of the hotspot closure. Over all years and 



