NOTE Weng and Block: Diel vertical migration in Alopias superaliosus 



223 



30° N 



82°W 



24°N 



166 



164 



162 



160 



158 



156°W 



Figure 1 



Deployment (A) and end-point (•) positions for the two pop-up satellite archival tags 

 attached to bigeye thresher sharks. Both tags surfaced on the programmed dates and 

 transmitted data to Argos satellites. Pressure sensors in the tags confirmed that the tags 

 remained attached to the sharks for the duration of the tracks. (A) In the Gulf of Mexico a 

 shark was tagged and released on 12 April 2000 and the tag surfaced on 10 June 2000. The 

 shark moved a straight-line distance of .320 km during the 60-day track. (B) In the Hawaiian 

 Archipelago a shark was tagged on 13 May 2003 off Kona, Hawaii, and the tag surfaced on 

 9 June 2003 northeast of French Frigate Shoals. The shark moved a straight-line distance 

 of 1125 km during the 27-day track. 



and upper thermocline between 10 m and 100 m (Fig. 2A). 

 The shark spent most of the daytime in deeper waters of 

 6°C to 12°C (70% [±4.4%], mean [±1 SE]), and most of the 

 nighttime in shallower waters from 20°C to 26°C (70% 

 [±2.7%], mean [±1 SE]) (Fig. 2B). A temperature-depth 



profile taken by the tag during the first day of the shark's 

 track closely matched a profile taken from the vessel with a 

 bathythermograph (Fig. 3A). The mean temperature-depth 

 profile for the 60-day track (Fig. 3B), when compared with 

 the shark's depth preferences (Fig. 2A), indicated that 



