650 



Fishery Bulletin 90(4), 1992 



with 6mg/kg oxytetracycline, but no flourescent mark 

 was found in the otohth or vertebrae. 



Abundance in relation to depth 



For bigeye tuna, the depth distribution of CPUEq 

 values (number of fish/1000 hooks with timers) was 

 similar in 1989 and 1990, with CPUEd highest at 

 360-400 m and relatively high at 200-400 m (Fig. 7). 

 Hooks with timers triggered before or at deployment 

 could not be subsequently triggered; therefore, they 

 were counted as hooks without timers when CPUEd 



was calculated (Table 4). The data from wider depth 

 ranges in both years were pooled to obtain sample sizes 

 (number of hooks with timers; Table 4) large enough 

 to determine whether significant differences existed 

 between depths (Fig. 8). For bigeye tuna, CPUEd 

 values were significantly higher at depths of >200m 

 than at depths of <200m (P<0.05, based on 95% CI 

 for the difference between proportions). Few (12%) of 



(n 

 0) 





o 

 o 



A 



o 

 o 

 o 



6 



a 



20 



16 



12 



8 



4 







4 

 3 

 2 

 1 

 

 8 

 6 

 4 

 2 

 



8 

 6 

 4 

 2 

 



16 



12 



8 



4 







Bigeye tuna 



^n rki 



Nm 



Yellowfin tuna 



li 



Striped marlin 



Ik 



^ 



Spearfish 



l^Jl 



Mahimahi 





O 

 CO 





o 

 r\i 



I 



o 

 oo 



o 



I 



o 



(V 



o 

 o 



o 



I I 



o 



o 

 o 



o 



CO 

 (M 



I 

 o 



o 



o 



I I 



-H ^ (V (V 



o 



CO 



o 



o 

 o 



I 

 o 



ro 



+ 

 o 

 o 



Hook depth (m) 



Figure 7 



Indices offish abundance vs. depth, calculated as the number 

 of fish caught/lOOO hooks with timers (CPUE,,) in ten depth 

 .strata. Indices for li)89 (open bars) and 1990 (crosshatched 

 bars) are based on fish captured while the gear was settled 

 (as confirmed by hook timers) (Table 4). 



(V 



in 



o 

 o 



o 

 o 

 o 



d 



Hook depth (m) 



Figure 8 



Indices of fish abundance vs. depth, calcu- 

 lated as the number of fish caught/ 1000 

 hooks with timers (CPUE,,) in four pooled 

 hook-depth strata. Indices for 1989 and 1990 

 combined are based on fish captured while 

 the gear was settled (as confirmed by hook 

 timers) (Table 4). Error bars indicate 95% 

 CI of the CPUEp values for each depth 

 category. 



