136 



Fishery Bulletin 100(1) 





Figure 1 



Blue marlin with pop-up satellite tag attached. The tag is located below the anterior portion of the dorsal 

 fin (within outlined area). 



racy). Water temperature was determined from tempera- 

 ture sensor readings by using a calibration provided by the 

 manufacturer Depth was estimated from water tempera- 

 ture values by using temperature and depth relationships 

 provided by the Bermuda Biological Station for Research, 

 which maintains an oceanographic sampling station (sta- 

 tion S) about 13 miles (24 km) to the southeast of the 

 island. 



Results and discussion 



Nine blue marlin. with estimated weights ranging from 

 150 to 425 lb (68 to 193 kg), were tagged between 25 

 July and 11 August 1999 (Table 1). Four specimens were 

 below the minimum size for tagging recommended by the 

 tag manufacturer (200 lb or 90.9 kg). Fight times ranged 

 between 15 and 35 minutes. Seven fish were initially 

 hooked in the jaw, and two were "foul-hooked" (i.e. outside 

 the jaw and mouth): one in the operculum and one in 

 the dorsal musculature. After tag placement, but before 

 release, one fish that was originally hooked in the jaw 

 became foul-hooked in the ventral musculature. Three of 

 the nine fish were transferred to the tagging vessel after 

 capture. Fish generally quieted down shortly after being 

 brought to the side of the vessel, which maintained a head- 

 way of 4-5 km/li during the tagging operation. Only a few 

 minutes were required to implant the satellite and con- 



ventional tags, photograph the fish, estimate weight, mea- 

 sure lower jaw fork length (most individuals), and remove 

 the hook. Condition of the fish varied, and three individu- 

 als required resuscitation prior to release. 



Eight of the nine tags became detached from their re- 

 spective host fish after five days, floated to the surface, 

 and transinitted to the Argos™"" satellite system. Based on 

 the first accurate location of the tags, net displacements 

 ranged from 40 to 134 nmi (72-248 km) with a mean lin- 

 ear displacement of 90 nmi (167 km) for each individual 

 (Fig. 2). These values are in the range reported for blue 

 marlin by Block et al. ( 1992) who followed six blue marlin 

 with acoustic transmitters for periods of one to five days. 

 They noted individual total movements (as opposed to net 

 displacements) of 253 km in about three days, 100 km in 

 five days, and four animals with movements of less than 

 100 km over the course of the respective tracking periods. 



Individual marlin in our study dispersed in all directions 

 from their point of release ( Fig. 2 ). The blue marlin tracked 

 by Block et al. ( 1992) and Holland et al. (1990) in Hawaiian 

 waters moved away from the point of capture in several dif- 

 ferent directions. However, the authors noted an orientation 

 of movements to the coastline of the Hawaiian Islands. Our 

 r-eleases were farther offshore and an affinity to the Bermu- 

 da coastline was not evident from the net movement data. 



Depending on the time of tag activation and the time of 

 tag deployment, up to 61 direct water temperature read- 

 ings, taken every two hours, were obtained for each blue 



