Squire: Aerial monitoring of abundance of pelagic fishes 



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Data reflecting number of sightings and tonnage ob- 

 served and its geographical distribution were used to 

 define the geographical limits of the core area for each 

 species. The core area for each species was determined 

 to include all or portions of the following 

 zones: northern anchovy, zones C,D,G,H; Pacific sar- 

 dine, zones C,D,G,H; Pacific bonito, zones C,D,G,J; chub 

 mackerel, zones C,D,G,H,I; jack mackerel, zones 

 D,F,G,H,I; bluefin tuna, zones I,K,L,N,P (Fig. 1). For 



each species, the number of block areas in each zone 

 comprising its core area and the total number of block 

 areas in its core area are given in Table 5. 



The core-area index is the mean of the T/BAF 

 weighted to account for differences in size of core area 

 within the zone to obtain a stratified mean (Cochran 

 1966). For each zone, the weight factor was the ratio 

 of the total number of block areas having high species 

 density in the zone to the total number of block areas 



