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Fishery Bulletin 96(3), 1998 
Figure 2 
X-ray radiograph of Alopias superciliosus used for age determination. B = birth mark, R = 
vertebral centrum radius. Radiating bands are indicated in even years: 2, 4, 6, 8, and 10. 
Analysis of covariance indicated that there is signifi- 
cant difference in PCL-R relationships between fe- 
male and male (P<0.05). Therefore, the PCL-R rela- 
tionships were expressed by sex as follows: 
female: PCL = 50.84 R° 494 (r 2 =0.75, n= 214), 
male: PCL = 48.91 R° 492 (r 2 =0.75, n=107). 
Growth bands included two types of growth zones, 
as shown on the x-radiographs. These varied with 
season; usually a more calcified zone (translucent 
zones in Fig. 2) represented growth in summer (Casey 
et al., 1985; Cailliet et al., 1986; Branstetter and 
McEachran, 1986). 
The vertebral bands numbered up to 21 and 20 for 
females and males, respectively. Owing to a lack of 
smaller specimens, the mean vertebral radii of bands 
I— III for females and I-V for males were interpolated 
from the relationship between vertebral radius and 
number of bands. The back-calculated length at band 
formation was able to be obtained by substituting 
the mean band radii (r.) for R in the PCL-R relation- 
ship (Table 1). 
The monthly change in vertebrae (MI ) indicated that 
MI reached its peak in February, 0.60 for males, de- 
creasing thereafter to its lowest value of 0.08 in June, 
and increasing thereafter (Fig. 4). This trend sug- 
gested that a vertebral band was formed once a year 
Centrum radius (mm) 
Figure 3 
Relationship between precaudal length and centrum 
radius of Alopias superciliosus. = female; • = male. 
in the period April to July. A similar trend was found 
for females. Following Tanaka and Mizue’s (1979) 
ageing criteria, we found that translucent zones (fast- 
growth zones) were formed between late spring and 
early summer, slow growth zones in winter, compa- 
