365 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
established in 1881 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Age and growth of the highly exploited 
narrownose smooth-hound ( Musteius schmitti) 
(Pisces: Elasmobranchii) 
Juan M. Molina (contact author ) 1 
Gabriela E. Blasina 2 
Andrea C. Lopez Cazorla 12 
Email address for contact author: jmmolina@criba.edu.ar 
1 Departamento de Biologia, Bioquimica y Farmacia 
Universidad Nacional del Sur 
San Juan 670, Primer Piso 
8000 Bahia Blanca, Buenos Aires, Argentina 
2 Instituto Argentino de Oceanografia 
Consejo Nacional de Investigaciones Cientificas y Tecnicas 
Florida 8000 (Camino La Carrindanga km 7,5) 
8000 Bahia Blanca, Buenos Aires, Argentina 
Abstract— The narrownose smooth- 
hound ( Musteius schmitti) is the 
most exploited elasmobranch of Ar- 
gentina, Brazil, and Uruguay and is 
considered endangered (IUCN Red 
List of Threatened Species). Provid- 
ing information on age and growth 
can improve efforts for conserva- 
tion of this species. Therefore, our 
objective was to provide accurate 
estimates of the age structure and 
growth parameters for narrownose 
smooth-hound from Anegada Bay, 
an important shark nursery area 
in Argentina. In vertebrae of nar- 
rownose smooth-hound, we observed 
a pattern of alternating opaque and 
translucent bands and a yearly peri- 
odicity in the deposition of this pat- 
tern. Ages determined from verte- 
bral band counts ranged from 0 to 
11 years. Calculated longevity and 
total natural mortality rates were 
20.87 years and 0.19/year for fe- 
males and 12.24 years and 0.26/year 
for males, respectively. This species 
reached a size of approximately 400 
mm in total length in the initial 
year of growth, and the age at first 
maturity was 7.61 years for females 
and 6.79 years for males. The slow 
growth and late age at maturity of 
the narrownose smoothhound indi- 
cate a need for additional conserva- 
tion measures to rebuild the popula- 
tion and achieve a sustainable fish- 
ery in the 3 countries in which it is 
distributed. 
Manuscript submitted 19 June 2016. 
Manuscript accepted 9 May 2017. 
Fish. Bull. 115:365-379 (2017). 
Online publication date: 8 June 2017. 
doi: 10.7755/FB.115.3.7 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
The Chondrichthyes make up a class 
of vertebrates that are usually de- 
scribed as late-maturing fish with 
a moderate-to-long life span and an 
extended gestation period that pro- 
duces a low number of developed 
offspring (Dulvy et al., 2008). Most 
chondrichthyans have limited geo- 
graphic distributions and gather in 
schools by age, sex, and reproductive 
states (Barker and Schluessel, 2005). 
The characteristic slow population 
growth of these elsasmobranchs ren- 
ders them highly vulnerable to fish- 
ing pressure (Dulvy et al., 2008; Cor- 
tes et al., 2010). Globally, chondrich- 
thyan fish populations are declining 
(Camhi et al. 1 ) — a fact aggravated 
by a lack of knowledge of the biology 
for many species. This lack of infor- 
mation makes identifying threats to 
1 Camhi, M. D„ S. V. Valenti, S. V. Ford- 
ham, S. L. Fowler, and C. Gibson 
(eds.). 2007. The conservation status 
of pelagic sharks and rays. Report of the 
IUCN Shark Specialist Group Pelagic 
Shark Red List Workshop, 78 p. IUCN 
Species Survival Commission Shark 
Specialist Group, Newbury, UK. 
conservation challenging, and design- 
ing appropriate management mea- 
sures almost impossible (Molina and 
Cooke, 2012). 
The narrownose smooth-hound 
{Musteius schmitti) is a small shark 
in the family Triakidae that attains 
a maximum total length (TL) of 110 
cm (Menni, 1985). Endemic to the 
southwest Atlantic Ocean, this shark 
occurs in waters over the continen- 
tal shelf, from coastal waters of less 
than 50 m to depths up to 120 m, 
throughout its range from southeast- 
ern Brazil to the Argentinean Pata- 
gonia (from 22°S to 47°S) (Menni, 
1985). This shark is known to mi- 
grate seasonally, in large numbers, 
between wintering grounds in south- 
ern Brazil and summering grounds in 
Argentina (Figueiredo, 1977; Vooren, 
1997). Seasonally, it also frequents 
estuaries, protected bays, and gulfs 
(Lopez Cazorla, 1987; Chiaramonte 
and Pettovello, 2000; Colautti et al., 
2010; Molina, 2013). 
The narrownose smooth-hound is 
the most exploited elasmobranch spe- 
cies (by both industrial and artisanal 
