Molina et al.: Age and growth of Mustelus schmitti 
375 
Size range (total lengths in millimeters), 
ficient ( K) of the von Bertalanffy growth 
genus from this study and other studies. 
Table 6 
maximum age measured ( £ max ), asymptotic length (LJ), and growth coef- 
Punction and growth performance index ($) for 9 species of the Mustelus 
Species 
Size range 
(mm TL) 
t max 
K 
1) 
Main reference 
Mustelus schmitti 
300-810 
11 
894 
0.06 
4.69 
This study 
Mustelus schmitti 
390-950 
16 
1000 
0.10 
5.00 
Hozbor et al. 6 
Mustelus schmitti 
250-960 
14 
1028 
0.08 
4.92 
Batista, 1988 
Mustelus antarcticus 
600-1700 
16 
2000 
0.12 
5.68 
Moulton et al., 1992 
Mustelus californicus 
235-1250 
9 
1500 
0.17 
5.58 
Yudin and Cailliet, 1990 
Mustelus henlei 
257-1000 
13 
1000 
0.22 
5.34 
Yudin and Cailliet, 1990 
Mustelus manazo 
680-800 
10 
2000 
0.10 
5.60 
Cailliet et al., 1990 
Mustelus mustelus 
360-1640 
24 
2000 
0.07 
5.44 
Goosen and Smale, 1997 
Mustelus walkeri 
410-1050 
16 
2000 
0.07 
5.44 
Rigby et al., 2016 
Mustelus asterias 
440-1120 
13 
1000 
0.19 
5.27 
Farrell et al., 2010 
Mustelus canis 
330-1320 
16 
1200 
0.29 
5.62 
Conrath et al., 2002 
2010; Rigby et al., 2016) (Table 6). To date, only one 
technical report and a M.S. thesis have described the 
age of narrownose smooth-hound (Batista, 1988; Hoz- 
bor et al. 6 ), and both of these publications report on 
studies that included in their sampling fish older than 
the fish that we captured (Table 6). It is likely that 
the larger and older fish in the Hozbor et al. 6 and Ba- 
tista (1988) studies account for the differences in range 
of ages between our study and theirs. The results of 
Hozbor et al. 6 are consistent with our results for the 
mean lengths at age for ages below 5 years, but, for 
animals >5 years, they report larger sizes at age. Ba- 
tista’s (1988) mean lengths at age, however, are greater 
than our estimations for almost all ages, but he did not 
provide length at age for age 0 and 1 and did not cap- 
ture males older than 7 years, which makes throughout 
comparisons difficult. 
In the population of narrownose smooth-hound in 
Anegada Bay, the rate of growth reflected in the incre- 
ments in the mean length at age was not consistent 
for some ages. A similar phenomenon was reported by 
Hozbor et al. 6 and Batista (1988), as well as in studies 
of other shark species (Cailliet et al., 1990, Goldman 
et al., 2006, Farrel et al., 2010, Fernandez-Carvalho 
et al., 2015). In a number of other studies on the age 
and growth of elasmobranches, tables of length at age 
are not presented (e.g., Kusher et al., 1992; Goosen 
and Smale, 1997; Smith et al., 2003, 2007; McFarlane 
and King, 2006; Booth et al., 2011; Joung et al., 2016; 
Lessa et al., 2016); therefore, it is difficult to determine 
whether this phenomenon is more or less universal for 
elasmobranchs or restricted to certain species. 
The narrownose smooth-hound attains an apprecia- 
bly smaller L*, and K than other representatives of the 
Mustelus genus, with the exception of the starspotted 
smooth-hound (M. manazo ) (Yudin and Cailliet, 1990; 
Table 6). In comparison with values reported by Ba- 
tista (1988) and Hozbor et al. 6 , who also worked with 
narrownose smooth-hound, values of L x and K from our 
study were also much lower. A possible explanation for 
this result is that the overall size distribution of the 
samples used by Batista (1988) and Hozbor et al. 6 in- 
cluded many large individuals (>850 mm TL), which 
were not present in our study, and only a low number 
of small individuals (<400 mm TL) both of which had 
a consequent effect on the asymptotic behavior of the 
VBGF. In these 2 studies, more than 60% of the indi- 
viduals were larger than 600 mm TL, but samples in 
our study only 20% of individuals were above that TL. 
As Campana (2001) points out, skewed size distribu- 
tions can introduce bias in age estimates, and differ- 
ences in size distributions between studies can accen- 
tuate such differences. 
Differences in the estimations of L„ and K can also 
arise from differences in the aging techniques em- 
ployed. Whereas Batista (1988) used whole vertebra 
and Hozbor et al. 6 employed sectioned vertebra, we 
used thinly sectioned slices. Despite their use of theo- 
retically more imprecise vertebra preparations, these 
authors could identify ages >than 11 years with their 
methods, indicating that the use of whole vertebrae by 
Batista (1988) or sectioned vertebrae by Hozbor et al. 6 
could be useful enough to study age for this species. 
Another possible explanation is the difference in 
the period of sampling. Hozbor et al. 6 sampled during 
2003-2004, almost 5 years before our research. Given 
the high level of fishing effort exerted on this species 
between 2004 and 2010 (Massa et al., 2006; Fernandez 
Araoz et al. 8 ), it is possible that natural populations 
experienced a reduction in their maximum length be- 
8 Fernandez Araoz, N. C., A. N. Lagos, and C. R. Carozza. 
2009. Asociacion fctica costera bonaerense ‘variado costero’ 
capturas declaradas por la flota comercial Argentina durante 
el ano 2008. INIDEP Inf. Tec. Of. 31, 26 p. [Available from 
website.] 
