Schaefer and Fuller: Movements, behavior, and habitat selection of Thunnus obcsus 



779 



10°N 



5°N 



CN 



5°S 



ICS 



10°N 



0°N 



5°S 



10°S 



no'w 



100°W 



90°W 



80°W 



110°W 



100°W 



gcw 



80°W 



Figure 9 



Movement paths of bigeye tuna derived from filtered geolocation estimates. The open squares are the release 

 positions at FADs. The open circles and solid squares are geolocation estimates for unassociated behavior and 

 behavior associated with a floating object, respectively, and the crosshairs are the recapture positions. The color 

 code for each fish, in each map, corresponds with the following tag number ( Al blue: 99-812. The dashed line, 

 between two geolocation estimates on 16 August and 27 September 2000, represents our inability to obtain 

 reliable estimates of latitude from light level data near the equinox, red: 99-793. The dashed line, preceding the 

 recapture position, represents our inability to obtain reliable estimates of latitude from light level data near 

 the equinox and the failure of the tag to log data on 3 October 2000. (B( blue: 99-804. The dashed line, preceding 

 the recapture position, represents the failure of the tag to log data on 9 October 2000. red: 99-826. The dashed 

 line, between two geolocation estimates on 20 August and 4 October 2000. represents our inability to obtain 

 reliable estimates of latitude from light level data near the equinox. The dashed line, preceding the recapture 

 position, reflects the failure of the tag to log data on 2.5 December 2000 iC I blue: 99-792. The dashed line, begin- 

 ning on 31 August 2000 preceding the recapture position, represents our inability to obtain reliable estimates 

 of latitude from light level data near the equinox, red: 99-787. (Di blue: 99-889. red: 99-869. 



Summerfelt, 1986; Baras and Westerloppe. 1999). In most 

 specimens, the ventral region of the body wall, where the 

 stalk protruded, did not appear to be completely healed. 

 A small, dark, circular crater was seen at the base of the 

 stalk — obviously a mark of irritation from the movement 

 of the stalk even after the tag body had been encapsulated 

 by flesh. Unless it is necessary to collect internal tempera- 

 ture data, the dorsal musculature is a potentially better 

 location for implanting archival tags, of appropriate size 

 and shape, for long-term deployment (Brill et al.-'). 



The long-term performance of the archival tags used in 

 our experiment was questionable. The bigeye tuna that 

 we studied pushed these tags to the limits of their design 



specifications by undergoing regular daily vertical forays 

 with fairly dramatic temperature and pressure fluctua- 

 tions, in addition to making the unexpected deep diving 

 events exceeding 1000 m. 



Of the 27 archival tags recovered to date, four of them 

 failed to collect light data because of apparent problems 



' Brill, R. W, K. Cousins, and P. Kleiber. 1997. Test of the 

 feasibility and effects of long-term intramuscular implantation 

 of archival tags in pelagic fishes using scale model tags and 

 captive juvenile yellowfin tuna {Thunnus albacares). NMFS 

 Admin. Rep. H-97-11.12 p. Southwest Fisheries Center Hono- 

 lulu Laboratory, National Marine Fisheries Service, NOAA, 

 Honolulu, HI 96822-2396. 



