Thompson et al.; Age distribution and growth of Senola dumerili 



367 



annuli 





Figure 4 



Photomicrograph of a sectioned sagitta IVom a 53-cm tagged and recaptured north- 

 central Gulf of Mexico greater amberjack obser\'ed under ultraviolet light. The fish was 

 at large for 160 days. Tetracycline mark = m; annuli are indicated by the arrows. 



greater amberjack were fitted to the von Bertalanffy 

 growth model (Fig. 7). Because there was no differ- 

 ence between male and female models (P>x^=0.496), 

 data were combined and resulted in 



L, - 138. 9( 1 - e-° 25't ^ 0.791) (^2=0.96, n - 552) 



Tag-recapture data obtained from the CGTP yielded 

 25 data points useful for comparison of growth rates, 

 and an additional six data points from our mark-re- 

 capture experiment. Predicted lengths fell along the 

 trajectory of a line where predicted lengths equalled 

 observed lengths (Fig. 7). The differences between 

 observed and predicted values were both positive and 

 negative. There was a tendency to under-predict fish 

 size above 80 cm recapture length. The growth of 

 tagged and recaptured fish provided additional sup- 

 port of our age estimation technique. 



Discussion 



Our observations of sex-related differences in maxi- 

 mum size of greater amberjack are consistent with 

 the findings of previous investigators. Burch (1979) 

 reported a maximum size of 145.0 cm for males and 

 of 155.5 cm for females and noted that the mean fork 



200 

 175 

 150 



>. 125 



o 



§ 100 



£ 75 



u. 



50 



25 







I 



I Females 



Q Males 



n Sex unknown 



<1 



4 6 8 



Age (yr) 



10 12 14 



Figure 5 



Estimated age-frequency histogram, identified by sex, of 

 northern Gulf of Mexico greater amberjack collected from 

 April 1989 to June 1992. 



length of females was greater than that of males of 

 the same age. Humphreys (1986) reported a maxi- 

 mum size of 106.0 cm for males and of 149.4 cm for 

 females. We found that the maximum size of males 

 (132.7 cm) was less than that of females (144.1 cm) 

 and that females represented 72% of the fish over 



