Schaefer and Fuller Movements, behavior, and habitat selection of TIn/nnus obesus 



767 



fish released with archival tags were observed to swim 

 rapidly down and away from the vessel after release, and 

 all appeared to be in excellent condition. 



Tag recoveries 



Twenty-nine of the 96 bigeye released with archival tags 

 were recaptured by 4 October 2001. Twenty-eight archival 

 tags were recovered, and the data from twenty-seven were 

 successfully downloaded and processed. The fish lengths, 

 release and recapture positions, and number of days at 

 liberty of the twenty-eight fish from which archival tags 

 were recovered are given in Table 1. Twenty-five of the 

 tags were recovered from fish caught by purse-seine ves- 

 sels during sets on FADs. Scientific observers were aboard 

 these purse-seine vessels, thus providing verification of 

 recapture information. Three fish, from which archival 

 tags (99-793, 99-812, and 99-865) were recovered, were 

 recaptured by longline vessels without scientific observers 

 aboard. 



Data processing 



Data were downloaded, decoded, and processed by using 

 software provided by the tag manufacturer (Wildlife Com- 

 puters, 2002). Light-level data were used to obtain daily 

 position estimates for each fish and ranges of uncertainty 

 about those estimates (Hill. 1994; Hill and Braun, 2001). 

 The accuracy and precision of the position estimates were 

 evaluated by calculating the differences between the 

 known recapture locations for 21 bigeye tuna, determined 

 by global-positioning systems (GPS) aboard the fishing 

 vessels, and the corresponding geolocation estimates. 



Two criteria were used for filtering (accepting or reject- 

 ing) daily geolocation estimates. The first was based on 

 the uncertainty associated with estimates of latitude for 

 the days of recapture, and the second was based on the 

 distance between geolocation estimates for consecutive 

 days. Those daily estimates in which the range between 

 the north and south errors was greater than 6° or the 

 location was farther than 4° in latitude from that for the 



