FISHERY BULLETIN: VOL. 85, NO. 3 



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I I All Schools 



^J Trackllne Schools 

 1-5 = Beaufort State 

 GS^Good Sun Conditions 

 PS- Poor Sun Conditions 

 ( ); Percent of Total Effort 



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12 3 4 5 

 Coastal Band 



12 3 4 5 



GS PS GS PS 



Offshore Band Coa&tal Offshore 

 Band Band 



Figure 5. — School detection rates for aerial data in the coastal 

 and offshore density bands for sea state and sun glare cate- 

 gories. 



server teams to determine relative effects upon 

 the density estimates. Team 1 and Team 2 

 searched approximately equal lengths of track- 

 line (46% and 54% of the effort, respectively). No 

 difference in performance of the two teams was 

 evident: their rates of detecting schools, both on 

 and off the trackline, and their estimates of school 

 densities were approximately equal (Fig. 6). 



Ship Data 



The rates of detecting dolphins were greater 

 during calm seas than during rough seas for the 

 ship surveys from 1979 through 1983 (Fig. 7). The 

 detection rate of dolphins during calm seas was 

 more than twice the rate during rough seas in 

 both the inshore and offshore areas. The ratio of 

 calm sea to rough sea detection rates was larger 

 in the offshore area than in the inshore area. 



The offshore area was surveyed during rougher 

 seas more than the inshore area (Fig. 8); seas 

 were calm in the offshore area during only 17% of 

 the effort as opposed to 35% for the inshore area 

 surveys (Fig. 7). Dolphin density was lower off- 

 shore as indicated by lower offshore detection 



rates than inshore rates during either calm or 

 rough seas (Fig. 7). The inshore-to-offshore-area 

 detection ratios were 1.5 during calm seas and 2.0 

 during rough seas. 



Sun glare had little effect on the shipboard esti- 

 mates during either year because poor sun condi- 

 tions occurred only during 6% of the 1982 and 8% 



^■° r □ All Schools 



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TEAM 1 TEAM 2 



Figure 6. — School detection rates and density estimates for 

 observer teams during the 1979 aerial survey. 



( )= % calm sea effort 

 in area 



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Figure 7. — Ratio of 1979-83 shipboard school detection rates for 

 different sea states (calm sea versus rough seal and area (in- 

 shore versus offshore). Detection rates computed with perpen- 

 dicular distance data truncated at 2.1 km. 



428 



