156 
Fishery Bulletin 111(2) 
100 125 150 175 200 
Fork length (cm) 
225 250 275 300 
Figure 5 
Total percent length-frequency distribution of Shortfin Mako (Isurus oxy- 
rinchus) collected from fishery-dependent (1981-2009) and fishery-inde- 
pendent (1993-2009) surveys conducted in the Southern California Bight. 
Vertical bars are placed in length bins of 5 cm along the x-axis, showing 
the range of fork lengths (FL) from 55 to 265 cm FL. Arrows show the 
approximate size at 50% maturity for males and females determined by 
Semba et al. (2011 ). 
should not be extrapolated beyond our size range and 
geographic area; however, our results indicate that 
growth patterns of juvenile and adult Shortfin Mako 
merit additional research. 
The differences in rates of band-pair deposition of 
Shortfin Mako among studies may be due to a number 
of factors, including study location, methods, and on- 
togeny. Rates of band-pair deposition of the Common 
Carp ( Cyprinus carpio) vary geographically among sim- 
ilar age classes of the same species; 
biannual deposition occurs in South 
Africa (Winker et al., 2010) and an- 
nual deposition occurs in Australia 
(Brown et al., 2004), exemplifying the 
importance of regional age validation. 
In one of the first Shortfin Mako 
aging studies, Pratt and Casey (1983) 
read silver-nitrate-stained, whole ver- 
tebral centra collected in the north- 
west Atlantic and suggested that 2 
band pairs were deposited annually, 
after noting that calculated growth 
under this assumption closely matched 
direct observations of growth over 
time for this species (especially for 
fish <200 cm FL). Pratt and Casey’s 
(1983) growth curves were generated 
from tag-recapture growth data col- 
lected in the field, temporal analysis 
of length-month information, and a 
vertebral age-based growth curve cor- 
roborated and compared with length- 
frequency mode analyses. 
In contrast, Cailliet and Bedford 
(1983) and Cailliet et al. (1983) used 
hard (high-frequency) X-radiography 
and silver nitrate staining of whole 
centra to elucidate banding patterns 
of Shortfin Mako in the northeast 
Pacific. The authors of both studies 
assumed that only 1 band pair was 
deposited annually and obtained a growth rate of about 
half the rate of that of Pratt and Casey (1983), but 
they did not test the assumption of 1 versus 2 band 
pairs per year. 
Campana et al. (2002) concluded that the hypothesis 
of a single band pair was the most consistent with the 
banding pattern obtained from a 21-year-old Shortfin 
Mako (328 cm FL) collected from the northeast Atlantic 
and aged with bomb-radiocarbon techniques. Ardizzone 
Table 2 
Estimates from the tag-recapture growth model with GROTAG for juvenile Shortfin Mako ( Isurus oxyrinchus ) in the eastern 
Pacific (n=62). Growth estimates from the length-frequency techniques (MULTIFAN and MIXDIST) also are included for the 
first 2 age classes. A’=Brody growth parameter, L oo =mean asymptotic length. 
Tag-recapture 
Length frequency 
Length frequency 
Parameter 
Symbol (unit) 
growth model 
(MULTIFAN) 
(MIXDIST) 
Growth rate 
g 85 (cm/year) 
29 
27 
36 
Si 3 o (cm/year) 
20 
23 
29 
K 
(per year) 
0.19 
0.17 
L„ 
(cm) 
231.03 
252.12 
Growth variability 
V 
0.31 
Mean measurement error 
m (cm) 
2.87 
Standard deviation measurement error 
s 
4.46 
Log likelihood 
X 
-235.8 
