Prince et al.: Movements and spawning of Tetrapturus albidus and Makaira nigricans 



661 



18.7 N 



18.8 N 



186N 



18.4 N 



18.2 N 



18.5 N 



68.3 W 



68.1 W 



68.6 W 68.4 W 68.2 W 68.0 W 

 Longitude 



x- 



18.5 N 



68.3 W 68.1 W 



Longitude 



Figure 1 



(A) Western part of Mona Passage off Punta Cana, Dominican Republic, showing the general area of the 

 recreational fishery for white marlin [Tetrapturus albidus, rectangle) and larval sampling (oval); (B) 

 April 23-24 sampling stations and (C) May 13-17 sampling stations. X = stations with no billfish larvae. 

 □ = stations with white marlin larvae, A = stations with blue marlin [Makaira nigricans) larvae, 

 • = stations with unidentified larval istiophorids. Larger markers indicate two billfish in sample; smaller 

 markers indicate one billfish in sample. Depth contours are in meters. 



during April and May were recorded at the surface, 

 whereas maximum depths ranged from 184 to 368 m 

 (Fig. 3). In one case (i.e., PC-WHM01), the minimum 

 and maximum temperatures and depths converged at 

 the surface, indicating constrained vertical movement 

 for this individual. However, in the majority of tracks 

 there was a clear separation of minimum and maximum 

 temperature and depth (e.g., PC-WHM02, Table 1), 

 indicating that active vertical movements were made 

 each day. Only one of the transmitting tags appeared 

 to pop-up prematurely (PC-WHM01, Fig. 3). This tag 

 disengaged from its white marlin host during a deep 

 dive (368 m) after 28 days at large (two days early). Al- 

 though the fate of this fish cannot be determined, death 

 is a distinct possibility. In general, all marlin spent a 

 high proportion of the time in which they were moni- 

 tored in the upper 25 m and at temperatures a28°C. For 



example, marlin spent from 50% to 60% of the time in 

 the first depth bin (0 to 25 m) and about 60% to 75% of 

 their time in the 28° to 30°C temperature bin (Fig. 4). 

 Both marlin species made dives down to 100-200 m or 

 more on a fairly consistent basis but generally stayed at 

 these depths less than 10% of the time (Fig. 4). 



One female adult white marlin, measuring 157 cm 

 lower jaw fork length, could not be resuscitated during 

 pop-up satellite tagging, presumably because of damage 

 caused by a hook that penetrated the stomach. Based 

 on length-weight conversion equations (Prager et al., 

 1995), the estimated weight of this fish was 21.6 kg 

 (47.2 pounds). The histologically examined ovaries con- 

 tained distinct postovulatory follicles, indicating that 

 spawning likely occurred within the previous 24 hours 

 (Fig. 5, upper panel). In addition, imminent spawning 

 (likely within the following 12 hours) was indicated by 



