496 



Fishery Bulletin 88(3), 1990 



Figure 3 



Yellowfin tuna YF8504 spent 8 daylight hours on the upcurrent side 

 of S FAD before moving away at night. The next morning it moved 

 to R FAD until disturbed by a school of porpoises, when it immediate- 

 ly took a direct course to the island dropoff, which it patroled for 

 the rest of the day. In this and subsequent figures, squares = hour- 

 ly position marks. 



tion within 50 m of the FAD for the remaining 8.0 

 hours of dayHght (Fig. 3). During this time the fish was 

 almost exclusively on the upcurrent side of the bouy. 

 At 2345 the fish left the FAD and moved offshore; by 

 sunrise the next day, it was 3.25 nmi from S FAD. The 

 fish then moved 3.0 nmi in a direct course to the 

 nearest adjacent FAD (R) arriving there at 0910. Once 

 there, it stayed extremely close to the FAD and in the 

 company of a school of other yellowfin tuna that could 

 be seen from the surface. At 1020 a group of porpoises 

 arrived and dove through the school of tuna, which ap- 

 peared to scatter in all directions. The tagged fish dove 

 and swam to the 40-fat.hom contour of the island, where 

 it stayed for the rest of the day. Contact was lost just 

 after sunset on the second night. 



Fish YF8305 (55 cm FL), after being tagged and 

 released at S FAD at 0705, swam for 4.0 hours on a 

 direct course to V FAD, approximately 10 nmi away 

 from the release point (Fig. 4). The fish spent 95% of 

 the next 5.0 hours moving around on the upcurrent side 

 of this FAD. In the late afternoon, the fish departed 

 the FAD and spent most of the night farther offshore, 

 moving in a 15-nmi loop before heading back toward 

 V FAD the following morning. Just after first light, 

 when the fish had returned to within 2 nmi of the FAD 



Figure 4 



Yellowfin tuna YF8305 departed S FAD immediately after release 

 at 0705 and took a direct course to the next nearest FAD, V (R was 

 off station at the time), where it patroled almost exclusively in the 

 upcurrent area (insert) before making an overnight excursion total- 

 ing 15 nmi. 



and appeared to be headed back even closer, the 

 transmitter was shed. 



The tracks of fish YF8406 (62.5 cm FL) and YF8501 

 (44.0 cm FL) were similar. During the daytime, both 

 fish stayed very close to their respective FADs (for 9 

 and 12 hours, respectively), and both were lost at 

 sunset in deteriorating sea conditions. Because there 

 was no evidence of transmitter failure, and exhaustive 

 searches at the FAD locations after dark failed to 

 relocate the signal, it is reasonable to assume that both 

 these fish were lost when they made sudden evening 

 departures from the vicinity of their respective FADs. 



Fish YF8302 (64 cm FL) was caught and tagged at 

 S FAD, but lost 5.0 hours later. When contact was lost, 

 the fish had departed the release site, but appeared to 

 be curving back toward the bouy. 



Fish YF8502 (74.5 cm FL) was similar to other FAD- 

 associated yellowfin tuna in that, for the first 5.0 hours 

 of the track (0600-1100), it stayed in close proximity 

 (within 100 m) to S FAD. However, it then moved 

 steadily away but was lost 12 nmi southwest of the 

 buoy due to equipment failure after 13.5 hours of track 

 and before any possible long-term trend had become 

 apparent. 



Fish YF8506 (75.25 cm FL) was caught near S FAD 

 at 0630. Unlike the other FAD-associated yellowfin, it 

 immediately began to move steadily away, maintain- 

 ing a constant southwest course for the next 17.5 

 hours, at which time the track was terminated (Fig. 5). 



