PEARSON, J. C. 



1941. The young of some marine fishes taken in lower 

 Chesapeake Bay, Virginia, with special reference to the 

 gray sea trout Cynoscion regalis (Bloch). U.S. Fish 

 Wildl. Serv., Fish. Bull. 50:70-102. 

 RICHARDS, C. E., AND M. CASTAGNA. 



1970. Marine fishes of Virginia's eastern shore (inlet and 

 marsh, seaside water). Chesapeake Sci. 11:235-248. 

 ROUNSEFELL, G. A., AND W. H. EVERHART. 



1953. Fisheries science: its methods and applications. 

 John Wiley and Sons, Inc.. N.Y., 444 p. 

 SPRINGFR, V. G„ AND K. D. WOODBURN. 



1960. An ecological study of the fishes of the Tampa Bay 

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 STEVENS, J. R. 



1962. Analysis of populations of sport and commercial 

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 I S DEPARTMENT OF COMMERCE. 



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 WELSH, W M . AND ( ' M BREDER. JR. 



1924. ( lontributions to the life history of Sciaenidae of the 

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Barbara J. Crowe 



2072 West Second Street, Apt. 11-E 

 Beach. MS .{9560 



growth of tunas (probably bluefin) was by Greek 

 fishermen nearly 2,000 yr ago as documented in 

 Aristotle's "Historia Anumalium" (Bell 1964). In 

 recent times, the aging of tunas has become much 

 more important and has been critiqued by 

 Hayashi (1958), Bell (1964), and Shomura (1966). 

 These reviews point to the problems and difficul- 

 ties in aging tuna. These problems and difficulties 

 appear to be more evident in aging bluefin tuna. 



Bluefin tuna are usually aged by counting 

 growth increments on their hard parts. Vertebrae 

 have provided acceptable ages (Rodriguez-Roda 

 1964; Butler 1971; Nichy and Berry 1976; Berry et 

 al. 1976), but the aging of large or "giant" (>250 

 kg) bluefin tuna is suspect because the outer in- 

 crements appear very close together. Otoliths have 

 also been used to study age and growth of bluefin 

 tuna (Butler et al. 1977). Berry et al. (1976) com- 

 pared otolith age estimates with vertebra esti- 

 mates and discovered a discrepancy. They found 

 corresponding marks on both vertebrae and 

 otoliths for the first 10 yr, but not thereafter, when 

 otoliths had more incremental zones. They 

 hypothesized that more than one incremental zone 

 was deposited yearly in otoliths after the first 10 yr. 



Daily increments in yellowfin tuna, Thunnus 

 albacares, and skipjack tuna, Katsuwonus 

 pelamis, otoliths were studied by Wild and Fore- 

 man (1980) and Uchiyama and Struhsaker (1981). 

 Taubert and Tranquilli (1982) used daily incre- 

 ments to verify annuli in the otoliths of large 

 mouth bass, Micropterus salmoides salmoides, and 

 it is proposed that an analogous investigation 

 would provide corroborative evidence for the an- 

 nual nature of outer major increments in giant 

 bluefin tuna otoliths. 



SCANNING ELECTRON MICROSCOPE 



EVIDENCE FOR YEARLY GROWTH ZONES IN 



GIANT BLUEFIN TUNA, THUNNUS THYNNUS, 



OTOLITHS FROM DAILY INCREMENTS 



Atlantic bluefin tuna, Thunnus thynnus, are 

 found throughout the Atlantic Ocean, the 

 Mediterranean Sea, and the Gulf of Mexico (Gibbs 

 and Collette 1967 ). Bluefin tuna are both commer- 

 cially and recreationally important. Thus, it is 

 important that the population dynamics of this 

 species be understood in order that international 

 policies can be developed. 



Age determination and subsequent growth es- 

 timation are critical for tuna management. How- 

 ever, confusion and controversy surround age es- 

 timation in tunas. The earliest record of age and 



404 FISHERY BULLETIN: VOL. 82, NO. 2, 1984. 



Methods and Materials 



Sagittal otoliths were collected in November 

 1978, from giant bluefin tuna which were reared in 

 the sea ranching program of St. Margaret's Bay, 

 Nova Scotia, Canada. Fish were weighed and mea- 

 sured (TL) and the otoliths were collected as de- 

 scribed by Caddy et al. (1976). All otoliths were 

 washed in water and stored dry. 



Whole otoliths from four fish were placed in 

 epoxy resin and sectioned on a Buehler Isomet 1 

 saw. Sections 200 /xm thick were acquired from the 

 region judged to contain the core. A diagrammatic 

 view of a cross section of a bluefin tuna otolith is 



1 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



