28 



Fishery Bulletin 89(1), 1991 



Figure 18 



Portion of a transverse section of a 

 vertebral centrum from a 2d-year 

 Galeorhinus galeus juvenile, showing 

 (a) focus, (b) hyaline cartilage, and (c) 

 calcified cartilage of intermedialia. 

 (1) 1st ring, (2) 2d ring, and (3) un- 

 calcified margin. (Haematoxylin, 50 x ) 



ing the widest possible range of TL at a given time of 

 the year, the data for June and July 1985 were pooled. 

 Von Bertalanffy growth parameters were obtained as 

 follows: females, k = 0.2 and L^ = 157cm (Rn = 612); 

 and males, k = 0.2 and L. = 157 cm (Rn = 429). 



Discussion 



The area of greatest uncertainty for interpreting and 

 measuring growth zones in shark centra is near the 



margin (Casey et al. 1985). Distinguishing the presence 

 of the last ring is a common problem (Casey et al. 1985, 

 Stevens 1975, Walker 1986). Using microradiography, 

 the margin can be easily observed in school shark 



