106 
Fishery Bulletin 109(1 ) 
Figure 1 
A sectioned vertebra of a 14-year-old wild spotted gully shark (Triakis 
megalopterus) tagged and injected with oxytetracycline hydrochloride 
seven years before recapture. 
Table 2 
Sex, capture locations and dates, total lengths (TL), and estimated ages of specimens of Triakis megalopterus tagged and injected 
with oxytetracycline hydrochloride (OTC) that exhibited fluorescing zones on vertebrae. All specimens were sampled off the 
southeast coast of South Africa. “Zones distal to OTC”=zones that fluoresced and that were distal to the site of the OTC injection. 
Gender 
Capture — > 
recapture 
locations 
Tagging 
date 
Recapture 
date 
Years 
at 
liberty 
Tagging 
length 
(mm TL) 
Recapture 
length 
(mm TL) 
Zones 
distal 
to OTC 
Total 
age 
Female 
Bayworld aquarium 
Feb 1999 
Dec 2000 
1.8 
1700 
1580 
1 
20 
Female 
Bayworld aquarium 
Nov 2001 
Jan 2003 
1.2 
1660 
1600 
1 
25 
Male 
Bayworld aquarium 
Apr 2002 
Dec 2002 
0.7 
1560 
1428 
1 
11 
Female 
De Hoop — > De Hoop 
Feb 1996 
Feb 1998 
2.0 
1111 
1140 
2 
12 
Male 
De Hoop — > De Hoop 
Sep 1996 
May 2003 
6.7 
1530 
1550 
7 
14 
Female 
Algoa Bay — » Knysna 
Mar 1998 
Mar 2005 
7.0 
950 
1250 
7 
14 
Undetermined 
De Hoop — > De Hoop 
Sep 2000 
May 2003 
2.7 
1020 
1140 
3 
10 
p- 4, AIC = 906.47; von Bertalanffy: p = 3, AIC = 904.56; 
logistic: p = 3, AIC = 912.89). The logistic model provided 
the worst fit of all three models considered. Although 
wild female sharks tended to grow larger and slower 
than males (Table 4, Fig. 3), there were no significant 
differences among any of the growth parameters (likeli- 
hood ratio test, P>0.05). Overall, the growth trajecto- 
ries of the tagged and recaptured sharks were consist- 
ent with the predicted von Bertalanffy growth model 
for combined sexes (Fig. 4). 
Age at maturity was calculated to be 10.9 years for 
males and 15.3 for females from the estimates of size 
of maturity for males (1320 mm TL) and females (1450 
mm TL) (Smale and Goosen, 1999). Natural mortality 
was estimated at 0.15/yr, the median of 0.10/yr, 0.16/yr 
and 0.17/yr, from the Pauly (1980), Floenig (1983), and 
Jensen (1996) models, respectively. 
Under the assumption of zero fishing mortality, the 
conditional intrinsic rate of increase parameter, r, was 
estimated at 0.00%/yr and was not significantly dif- 
ferent from zero based on the 95% confidence inter- 
val (P>0.05) (Table 5). The average age of mothers of 
newborn individuals in the stable-age population was 
estimated at 18.76 years, and the average number of 
