capable of permanently storing important ecologi- 

 cal information since they are not susceptible to 

 resorption (Mugiya and Watabe 1977). Otoliths 

 have been shown to be the more accurate method 

 of age determination in several fish species (Six 

 and Horton 1977; Kimura et al. 1979). Otoliths are 

 probably the most accurate means of age resolu- 

 tion in bluefin tuna. 



In conclusion, the observation that micro- 

 increments in the sagittae of giant bluefin tuna 

 about 365 in number for each outer major incre- 

 ment verifies the annual nature of these struc- 

 tures and strongly suggests that the micro- 

 increments are daily. Although it is not feasible to 

 view large numbers of tuna otoliths by SEM 

 techniques, the application of such techniques can 

 provide answers to important biological questions. 



Acknowledgments 



Thanks are due to P. Hurley, Biological Station, 

 St. Andrews, New Brunswick, for providing the 

 samples, to J. Bell for critical review and discus- 

 sion, and to R. Kawamoto for artistic work. 



This work, a part of the "Program Development, 

 Management, and Administration" project 

 (PM/M-1), is the result of research sponsored by 

 the University of Hawaii Sea Grant College Pro- 

 gram under Institutional Grant NA79AA-D- 

 00085 from NOAA, Office of Sea Grant, Depart- 

 ment of Commerce, and NSF grant OCE-8208441. 



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