speed of the ship was 4 knots; (2) the ship was not 

 permitted to go astern because the cavitation bub- 

 bles from the propeller would completely block the 

 tag signals; (3) the distance between tag and ship 

 could only be estimated from the strength of the 

 signals from the tag. 



A bathythermograph cast was made every 4 h to 

 obtain temperature-depth profiles. These profiles 

 and the temperature-dependent pulse rates of the 

 tags enabled estimation of swimming depth of the 

 marlin. 



RESULTS 



Five blue marlin were tagged and tracked, one on 

 14-15 July 1971 and four between 25 and 28 July 

 1972. Dates, size of fish, duration of tracking and 

 remarks on each fish are listed in Table 1. 



The first tagged marlin was tracked for 22 h 25 min 

 before an equipment breakdown forced a stop. The 

 second fish was in doubtful condition when released. 

 It was difficult to track and contact with it was lost 

 after an hour. The third marlin was tracked for 5 h 

 22 min before it was lost because of a tactical 

 error. Marlin #4 was abandoned after 7 h because it 

 remained stationary on the bottom soon after it was 

 tagged. After 2 h of swimming the fifth marlin also 

 went to the bottom. 



Path 



The paths of the marlin tracked are shown in Fig- 

 ures 2 and 3. The path of the last marlin is, of course, 

 of questionable value as the fish lived only 2 h after 

 being tagged. A feature that stands out is that all 

 three marlin moved in a northerly direction . North of 

 Keahole Point there is only one instance where the 



Table 1. — Data on blue marlin tagged. 



Marlin 



Estimated 





Duration 





No. 



weight 



Date tagged 



tracked 



Remarks 





kg (lb) 





h 





1 



270 (600) 



7/14/71 



22V4 



Lost — equipment 

 failure. 



2 



225 (500) 



7/25/72 



1 



Lost — no 

 movement. 



3 



135 (300) 



7/25/72 



5>/2 



Lost — tactical 

 error. 



4 



160 (350) 



7/27/72 



7'/2 



Abandoned — no 

 movement. 



5 



70 (150) 



7/28/72 



8 



Abandoned — no 

 movement after 2 h. 



Figure 2. — Path of blue marlin tracked in 1971. Numbers 

 along track denote hour of day. 





O ' l 2 3 4 5 



6 



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s 





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 r^^o-lijTOO^jgoq' / 



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f^ 



19" 



-1440 TAGGED {-. 

 •17/25/72) . \". 

 1 \\\ 

 \ dlTO 







J HAWAI 1 





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, 1629 TAGGED . 

 J17/28/72) 



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C KEAHOLE PT. 





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Figure 3. — Path of two blue marlin tracked in 1972. Num- 

 bers along track denote hour of day. 



267 



