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 

 marl in. 



RESULTS 



Five blue marlin were tagged and tracked, one on 

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

 1972. Dates, size offish, 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 I. — Data on blue marlin tagged. 



Marlin Estimated Duration 



No. weight Date tagged tracked 



Remarks 



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

 along track denote hour of day. 



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

 bers along track denote hour of day. 



267 



