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Fishery Bulletin 103(4) 



anecdotal information about gravid fish, prompted the 

 present examination of adult movements in a potentially 

 important, but as yet unconfirmed, spawning location. 

 The present study was conducted off Punta Cana, 

 Dominican Republic, during April and May 2003. Objec- 

 tives were 1) to characterize the horizontal and vertical 

 movement of adult white marlin captured from the area 

 using pop-up satellite archival tags (PSATs) and 2) to 

 investigate by larval sampling, whether marlin were 

 reproducing at this location. 



Materials and methods 



Deployment of PSAT tags on adult marlin was conducted 

 from a 17-m charter fishing vessel by using standard 

 trolling gear (9/0 long-shaft J hooks) and dead bait. 

 Wildlife Computers Inc. (Redmond, WA) PAT 3 model 

 tags were used. This tag allows the user to program 

 pop-up date, sampling interval, criteria for premature 

 release, bin demarcations for sampling temperature and 

 pressure (depth), as well as transmission and memory 

 priorities. These tags were programmed to sample depth 

 (pressure), temperature, and light once every minute 

 and the depth and temperature records were summa- 

 rized into histograms at 3-hour intervals. A pressure- 

 activated mechanical detachment device was also used 

 which severs the monofilament tether at a depth of about 

 1500 m — well before the 2000 m depth at which the tag 

 is crushed and disabled. This feature helps prevents data 

 loss in the event of fish mortality. 



All PSAT tags were rigged similarly according to 

 methods described by Graves et al. (2002). Billfish han- 

 dling and tagging procedures and associated devices 

 reviewed by Prince et al. (2002a) were also used. The 

 target area for tag placement was about 4 to 5 cm ven- 

 tral to the dorsal midline, adjacent to the first several 

 dorsal spines. An effort was made to insert the anchor 

 through the dorsal midline, pterygiophores, and connec- 

 tive tissue to a depth just short of the anchor exiting 

 the opposite side of the fish. In addition, a conventional 

 streamer tag (series PS) was placed in the fish well 

 posterior to the PSAT tag, according to standard pro- 

 cedures (Prince et al., 2002a). 



Two devices were used during tagging which tend 

 to reduce stress in captured fish and to aid in proper 

 tag placement. The first was a "snooter" (a wire snare 

 housed in a 1.5-m PVC tube), which secures to the up- 

 per bill and allows the tagger to maintain control of the 

 fish while its head remains beneath the water during 

 the tagging procedure (Prince et al., 2002a). The second 

 was a small hook "gaff" (a long shaft 9/0 hook with 

 point and barb removed) to manipulate the position 

 of the fish in relation to the tagging vessel. Captured 

 fish were resuscitated for 3 to 15 minutes, depending 

 on their apparent state of exhaustion, by moving the 

 vessel ahead at two to three knots while maintaining 

 control of the fish with the snooter. State of exhaustion 

 was inferred from coloration, fight time, and signs of 

 sluggish movement. 



One white marlin died during tagging and was re- 

 tained for examination of its reproductive status. Whole 

 or quarter transverse sections of ovarian tissue were 

 preserved in 10% formalin. Preparation for histologi- 

 cal analysis followed McBride et al. (2002). Histologi- 

 cal determination of spawning activity was based on 

 oocyte classification and the presence of postovulatory 

 follicles (Wallace and Selman, 1981; Hunter and Mace- 

 wicz, 1985; Hunter et al., 1992). 



Once adult marlins were located for tagging, neuston 

 sampling was conducted from the same fishing vessel 

 with methods similar to those reported by Serafy et 

 al. (2003). In the present study, ten-minute daytime 

 tows were performed with two neuston nets. Both nets 

 had 1000-fim mesh and were attached to 1 mx0.5 m or 

 2 mx 1 m rectangular aluminum frames. Water volume 

 filtered was measured with a mechanical flow meter; 

 station coordinates and water column depth measure- 

 ments were obtained by using a hand-held geographical 

 positioning system and depth sounder. Neuston collec- 

 tions were made along a series of transects that covered 

 the general area of the recreational fishery for white 

 marlin at this location (Fig. 1). The neuston samples 

 were initially stored in 150 proof white rum. Upon 

 returning to the laboratory (i.e., within 24-96 hours) 

 they were transferred to 95% ethanol. Billfish larvae 

 were sorted from the samples and measured by using 

 Image Pro image analysis software (Image Pro Plus, 

 version 4.5, Media Cybernetics, Inc. Silver Spring, MD). 

 Larval identification was conducted by using restriction 

 fragment length polymorphism analysis of the nuclear 

 MN32-2 locus following the methods of McDowell and 

 Graves (2002). 



Results 



Seven white marlin and one blue marlin were tagged 

 with PSAT tags off Punta Cana, Dominican Republic, 

 between April 23-24 and May 14-17 2003 (Table 1). 

 All but two tags were programmed to pop-up after 30 

 days; the exceptions were 40-day deployments for one 

 white marlin and one blue marlin. One of eight PSATs 

 (deployed on a white marlin) failed to transmit data and 

 one white marlin died prior to release (see below) from 

 hook-related injuries. The displacements of the six white 

 marlin from the original point of release ranged from 

 31.7 to 267.7 nmi (58.7 to 495.8 km), whereas the dis- 

 placement for the blue marlin was 219.3 nmi (406.2 km. 

 Table 1, Fig. 2). Displacements per day for white marlin 

 ranged from 1.1 to 7.2 nmi (average of 3.4 nmi). Cor- 

 responding daily displacement for the one blue marlin 

 was 5.48 nmi (Table 1). 



The minimum and maximum depth and temperatures 

 monitored for the seven PSAT-tagged marlin during 

 the 30- and 40-day deployments showed that on most 

 days, marlin visited depths 2IOO m (Fig. 3). Minimum 

 temperatures ranged from 16.8° to 20.6°C, whereas the 

 maximum temperatures ranged from 28.2° to 30.0°C. In 

 all cases, the minimum depths for each fish monitored 



