138 



Fishery Bulletin 100(1) 



Sft-W 



63°W 



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32°N 



63°W 



Figure 2 



Map showing points of release (squares) and points of recovery (end of straight lines) for 

 eight of nine blue marlin equipped with pop-up satellite tags near Bermuda, 25 July-11 

 August 1999. The pop-up satellite tag number for each fish and straight line distance 

 between point of release and geolocation where tag transmitted data to the Argos satellite 

 (given in parentheses) are provided. 



nine blue marlin caught on recreational gear survived for 

 five days following capture, tagging, and release events. 

 The net movement data indicated a broad dispersal of the 

 eight fish in different directions that cannot be explained 

 by local currents. In contrast to the differing direction of 

 movement, the net displacements of the eight fish were 

 fairly similar. The mean displacement of 89.25 nmi over 

 a five-day period, compares favorably with blue marlin 

 swimming velocities of 1-2 nmi/h reported from acoustic 

 tracking studies (Holland et al., 1990) and is consistent 

 with the constant slow swimming of the individuals. Al- 

 though currents could have accounted for some of the net 

 displacement, inclinometer values indicated that all eight 

 individuals were actively swimming. 



The water temperature measurements indicated that 

 each blue marlin actively undertook dives into cooler wa- 

 ter throughout the course of the five days. All eight in- 

 dividuals spent the vast majority of their time in waters 

 with temperatures of 26°C or greater, and no readings be- 

 low 22°C were recorded. 



The successful data recording, tag detachment, and 

 transmission of eight of the nme pop-up satellite tags begs 

 the question of what happened to the one tag that failed to 

 report. It is not possible to distinguish between the postre- 

 lease mortality of a tagged blue marlin and the mechani- 

 cal failure of a pop-up satellite tag. If a marlin dies and 

 sinks in deep water, the attached pop-up satellite tag even- 

 tually will be crushed by increasing hydrostatic pressure. 



