778 



Fishery Bulletin 100(4) 



(distributions and visible (disk area of the moon. The pat- 

 terns in average daytime depths for 5 of the 8 fish showed 

 a significantly shallower depth distribution for a 3-day 

 period surrounding the full moon (190 m) compared to 

 the other 26 days of the lunar cycle (221 m). There was no 

 apparent pattern, and the correlation coefficient (7-=0.15, 

 P>0.05) was not significant for the average daytime depth 

 for all 22 bigeye tuna in relation to the visible disk area of 

 the moon (Fig. 12B). 



Discussion 



The results obtained in our study are useful for evaluat- 

 ing fine- to large-scale horizontal and vertical movements, 

 behavioral patterns, and habitat characteristics on spatial 

 and temporal scales previously undocumented for bigeye 

 tuna. Movement paths, residence times at FADs, and 

 habitat selection are essential for understanding the ecol- 

 ogy of this species, and should be incorporated into stock 

 assessment models to evaluate its vulnerability to various 

 modes of fishing. 



In addition to the 96 bigeye tuna released with archival 

 tags, we released 101 bigeye tuna, in the same area and 

 time period, with conventional plastic dart tags only. To 

 date, 29 (30%) of the fish with archival tags and 22 (23%) 

 of these with conventional tags have been confirmed as 

 recaptured. The difference between these percentages was 

 not significant (P>0.05), indicating that tagging mortality 

 was probably no greater for the fish with archival tags 

 than the fish with conventional tags. 



Several of the archival tags were removed from recap- 

 tured bigeye tuna by members of the scientific staff of the 

 Inter- American Tropical Tuna Commission (lATTC). All 

 but two of the tags were situated in the peritoneal cavity, 

 in the general area where they were implanted, and were 

 apparently encapsulated by fibrous connective tissue. Of 

 the two other tags, one had apparently been invaginated 

 into the lumen of the stomach and the other into the lu- 

 men of the intestine. Apparently the fish were attempting 

 to expel these foreign bodies from their peritoneal cavities. 

 Transintestinal expulsion of surgically implanted trans- 

 mitters by fish was previously considered an exceptional 

 phenomenon, except in the case of catfish (Marty and 



