interesting information on the age of 

 tiie biuefin tuna, but Frade showed 

 that growth lines were clearly indi- 

 cated on scales of young individuals. 

 The experts concluded that scales 

 were not useful for determining 

 growth in this species, except for 

 young individuals. 



Spagnolio (1938) estimated ages 

 of from 3 to 6 years from scales of 

 biuefin tuna caught in traps off south- 

 em Italy and northeastern Sicily. She 

 presented illustrations of these scales 

 but did not report the sizes of the 

 fish. She concluded that readings 

 from scales should be checked against 

 readings from vertebrae of the same 

 individual. She maintained that if the 

 method were validated, scales would 

 be preferable to vertebrae for deter- 

 mining ages of small biuefin tuna, up 

 to 40-58 kg or 5-6 years of age, since 

 scales were easier to collect and to 

 examine than vertebrae. Spagnolio 

 used scales from the caudal and lat- 

 eral parts of the body, rejecting those 

 from the corselet because they were 

 too thick and opaque. The scales 

 which she used were preserved in 

 formalin, and later were soaked in 

 water or an alcohol solution or glyc- 

 erine before examination. She found 

 no marked advantage in using either 

 of the last two fluids instead of wa- 

 ter. 



Westman and G ilbert ( 1 94 1 ) and 

 Westman and Neville (1942) used 

 readings of annuli on scales, as well 

 as analyses of length frequencies, to 

 determine ages of young (1-7 year 

 old) biuefin tuna taken off Long Is- 

 land, New York, during the summers 

 of 1938 and 1941. These authors also 

 offered tentative age determinations 

 from scales for a few much larger 

 biuefin tuna, up to 250 cm and 275 

 kg, with an estimated age of about 1 8 

 years. They used carefully selected 

 thin and round scales from the side 

 of the body, just below the lateral 

 line in the area below the base of the 

 second dorsal fin. Projected impres- 

 sions of the scales facilitated their 

 readings of those with more than five 

 annuli. 



Mather and Schuck (1960) esti- 

 mated ages of 0-4 years from scales 

 of biuefin tuna taken off the north- 

 eastern United States during several 

 summers. They relied more heavily 

 on length frequencies for studying 

 the growth of young individuals, 

 however, and on vertebral annuli for 

 the older ones. These authors used 

 scales from the general part of the 

 tuna's body where Westman and Gil- 

 bert ( 1 94 1 ) and Westman and Neville 

 (1942) collected theirs. They made 

 impressions of the scales on cellu- 

 loid (Arnold 1 95 1 ), and counted an- 

 nuli on magnified projections of these 

 impressions. 



None of the above authors used 

 the large and thick scales of the corse- 

 let for age determinations, but F.S. 

 Russell mentioned (personal commu- 

 nication) that he had found a pos- 

 sible method of determining ages 

 from these scales. He found that they 

 were built up of lamina, like the pages 

 in a book, which might represent 

 years of growth. These lamina could 

 be separated after the scales had been 

 soaked in a weak solution of acetic 

 acid. 



The most important use of scale 

 readings in aging biuefin tuna has 

 been in validating determinations 

 made by other methods (Westman 

 and Neville 1942, Mather and Schuck 

 1960). 



b. Vertebrae 



F. de Buen (1925) estimated, by 

 counting its vertebral rings, that a 

 male biuefin tuna 206 cm long (from 

 snout to tips of caudal) and weighing 

 1 19 kg was 12 years old. This fish 

 was caught July 4, 1923. in the 

 Barbate trap near Cadiz, Spain. 



Sella (1929a) presented mean 

 lengths and weights of Mediterranean 

 biuefin tuna for ages 1-14, as esti- 

 mated by counting the rings in the 

 centra of vertebrae. This was the first 

 study which described the growth of 

 biuefin tuna through most of the size 

 range ordinarily encountered 



At the "Conference of experts" 

 (Anonymous 1932b), Sella and the 



other experts discussed the use of 

 vertebrae forage determination. Sev- 

 eral methods of preparing vertebrae 

 for examination were described, and 

 it was noted that they could be exam- 

 ined without special preparation. He 

 described three instruments which he 

 used in the study of vertebrae and 

 stated that the annuli were generally 

 better defined in vertebrae from the 

 caudal trunk. Heldt reported that, in 

 each of five biuefin tuna of different 

 sizes which he had examined, the 

 number of annuli on each of the ver- 

 tebrae was the same. He also noted 

 that double rings, which should not 

 be counted as two years, sometimes 

 occurred. Sella and F. de Buen main- 

 tained that the vertebral rings repre- 

 sented years of age, but the latter 

 noted that, because of the time of 

 spawning, the first ring did not cor- 

 respond exactly to one year. Frade 

 reported finding 16 vertebral annuli 

 for a 263 cm fish, which exceeded 

 the maximum age reported by Sella 

 (1929a). 



Several workers reported on the 

 growth of biuefin tuna from different 

 areas as determined from readings of 

 vertebral annuli in the period 1956- 

 1962. These include Hamre (1958, 

 i960) (Norway), Rodriguez-Roda 

 (1960) (Spain), Vilela and Pinto 

 ( 1 958), Vilela ( 1 960), and Frade and 

 Vilela (1962) (Portugal), and Mather 

 and Schuck (1960) (northeastern 

 United States). Mather and Schuck 

 used the technique of Galtsoff ( 1 952) 

 to stain many of the vertebrae which 

 they used for age determinations. 

 Rodriguez-Roda (1964a) presented 

 thorough mathematical interpreta- 

 tions of his I960 results. 



Butler ( 1 97 1 , 1975) counted the 

 rings in the vertebrae of large biuefin 

 tuna taken in Canadian waters in 1 966 

 and in 1974 and estimated their ages 

 as 1 1 to 22 or more years. Myklevoll 

 used this method to determine the 

 ages of biuefin tuna taken in Norwe- 

 gian waters in 1974 (Caddy and But- 

 ler 1976). These estimates ranged 

 from 1 4 to 2 1 years. 



