Prince et al 



Movements and spawning of Tetrapturus albidus and Makairo nigricans 



665 



also coincided in time and space with 

 the fishing activity of the recreational 

 white niarlin fishery that has operated 

 each spring at this location for over 40 

 years. From PSAT tag data, adult white 

 and blue marlin caught at this time and 

 in this area appeared to exhibit similar 

 vertical and horizontal movement pat- 

 terns in terms of time at depth, time 

 at temperature, average horizontal dis- 

 placement per day, net horizontal dis- 

 placement, and direction of dispersion 

 (compass heading). 



Movements 



Average displacement per day is one 

 possible measure to characterize daily 

 horizontal movement activity. We exam- 

 ined this metric in other PSAT stud- 

 ies on marlin and compared them with 

 our results (Fig. 7). Graves et al. (2002) 

 monitored eight blue marlin with PSAT 

 tags caught off Bermuda in July 2000 for 

 periods of 5 days each and reported net 

 displacement vectors ranging from 7.8 to 

 26.4 nmi/day (mean displacement for the 

 eight fish was 17.5 nmi/day). Kerstetter 

 et al. (2003) also monitored blue marlin 

 during the summer months with PSAT 

 tags in the northwest Atlantic (for 5 and 

 30 days) and found that displacements 

 ranged from 15.1 to 39.2 nmi/day (mean 

 for six fish was 22.9 nmi/day). Net dis- 

 placement findings (17.5 and 22.9 nmi/ 

 day), presumably for blue marlin spawn- 

 ing times (summer months) from these 

 two studies were roughly 5 to 6.5-fold 

 higher than the average displacements 

 for white marlin reported in our present 

 study (about 3.3 nmi/day) and were 3 to 

 4-fold higher than the average displace- 

 ment for the one blue marlin monitored 

 in our study (Fig. 7). A recent report 

 (Graves and Horodysky 4 ) has provided 

 displacement movements of white marlin 

 monitored with PSAT tags for 5 to 10 day 

 periods from three different areas in the 

 Northwest Atlantic during May (Punta 

 Cana, Dominican Republic), August- 

 September (U.S. Mid-Atlantic waters), 

 and November (La Guaira, Venezuela) 

 2002. Only the work in Punta Cana was 

 conducted during the presumed spawn- 

 ing season for white marlin. Average 

 displacements for these areas were 9.6 



Figure 5 

 Upper panel. A postovulatory follicle (POF), advanced yolked oocyte 

 (AYO), and follicle (F) are shown in section of gonad from a female 

 white marlin (Tetrapturus albidus) sampled off Punta Cana, Dominican 

 Republic, 16 May 2003. The presence of POFs indicates recent spawning 

 (likely within 24 hours). Lower panel. The labeled oocyte has begun 

 final oocyte maturation, as indicated by the migration of the nucleus 

 (Nu) to the periphery and yolk coalescence (YC). Both of these steps are 

 among the series of events initiated hormonally that occur just prior to 

 spawning (likely within 12 hours). 



4 Graves, G. E., and A. Z. Horodysky. 2002. Progress 

 report. Use of pop-up satellite archival tags to study sur- 

 vival and habitat utilization of white marlin released from 



the recreational fishery, 34 p. Virginia Institute of Marine 

 Science, College of William and Mary, Gloucester Point, VA 

 23062-1346. 



