468 
NOAA 
National Marine 
Fisheries Service 
Abstract— The bigeye thresher (Alo- 
pias superciliosus) is a pelagic shark 
captured as bycatch in pelagic long- 
line fisheries. Important informa- 
tion on its biology is still missing, 
especially from the Atlantic Ocean. 
In all, 546 vertebrae collected by 
fishery observers between 2007 and 
2009 were used to estimate age and 
growth parameters for this spe- 
cies in the Atlantic Ocean. The size 
composition was 102-265 cm fork 
length (FL) for females and 94-260 
cm FL for males. The estimated ages 
ranged from 0 to 25 years for both 
sexes. From the 5 growth models 
used, the 3-parameter von Berta- 
lanffy growth model, reparameter- 
ized to estimate length at birth (Lq), 
produced the best results. The esti- 
mated parameters were asymptotic 
maximum length (L; n f)=284 cm FL, 
growth coefficient (k )=0. 06/year, 
and Lo=109 cm FL for females and 
L; n f=246 cm FL, k=0. 09/year, and 
Lo=108 cm FL for males. Although 
differences between hemispheres 
indicate slower growth rates in the 
South Atlantic Ocean, these differ- 
ences may also have been caused 
by the lower sample size and larg- 
er specimen sizes for the Southern 
Hemisphere. The estimated growth 
coefficients are among the lowest 
found for the Alopiidae, highlighting 
the bigeye thresher’s slow growth 
and consequent low resilience to 
fishing pressure. 
Manuscript submitted 5 September 2014. 
Manuscript accepted 1 September 2015. 
Fish. Bull. 113:468-481 (2015). 
Online publication date: 22 September 2015. 
doi: 10.7755/FB.113.9 
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. 
Fishery Bulletin 
& established 1881 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Modeling age and growth of the bigeye thresher 
(Alopias superciliosus) in the 
Atlantic Ocean 
Joana Fernandez-Carvalho 1 - 2 
Rui Coelho (contact author ) 1 ' 2 
Karim Erzini 2 
Miguel N. Santos 1 
Email address for contact author: rpcoelho@ipma.pt 
1 Instituto Portugues do Mar e da Atmosfera (IPMA) 
Avenida 5 de Outubro s/n 
8700-305 Olhao, Portugal 
2 Centro de Ciencias do Mar (CCMAR) 
Universidade do Algarve, FCT Ed. 7 
Campus de Gambelas 
8005-139 Faro, Portugal 
The bigeye thresher (Alopias super- 
ciliosus) is a pelagic shark distin- 
guished by its long, whiplike upper 
caudal lobe, large eyes, and deep 
horizontal grooves above the gills 
(Bigelow and Schroeder, 1948). It 
has a worldwide distribution in the 
Atlantic, Pacific, and Indian oceans 
and Mediterranean Sea, ranging 
from tropical to temperate regions in 
primarily oceanic epipelagic waters, 
but it sometimes approaches coastal 
waters (Stillwell and Casey, 1976; 
Compagno, 2001; Nakano et ah, 2003; 
Weng and Block, 2004; Smith et al., 
2008; Cao et al., 2011). 
Like other members of the order 
Lamniformes, the bigeye thresher 
is an aplacental, viviparous species 
with intrauterine oophagy, bearing 
2-4 pups per litter, resulting in an 
extremely low fecundity (Moreno and 
Moron, 1992; Gilmore, 1993; Chen 
et al., 1997; Compagno, 2001). This 
species has been described as hav- 
ing one of the lowest intrinsic rates 
of population increase among elas- 
mobranchs, highlighting its high 
vulnerability to exploitation (Smith 
et al., 1998; Chen and Yuan, 2006; 
Cortes, 2008). According to the Inter- 
national Union for the Conservation 
of Nature (IUCN) Red List Criteria, 
this species is classified as “vulner- 
able” globally and “endangered” in 
the northwestern and western cen- 
tral Atlantic Ocean (Amorim et al., 
2009). Furthermore, this species was 
classified as being at high risk in an 
ecological risk assessment of pelagic 
sharks caught in pelagic longlines in 
the Atlantic Ocean, highlighting the 
urgent need for better basic biologi- 
cal information on this shark (Cortes 
et al., 2010). 
In the Atlantic Ocean, the pelagic 
longline fisheries that target sword- 
fish ( Xiphias gladius ) also capture 
several species of pelagic sharks as 
bycatch (Moreno and Moron, 1992; 
Buencuerpo et al., 1998; Megalo- 
fonou et al., 2005; Coelho et al., 
2012). Bycatch of bigeye thresher by 
these fisheries has been estimated at 
around 0.2% of the total shark by- 
catch for the entire Atlantic Ocean 
(Mejuto et al., 2009). The Interna- 
tional Commission for the Conser- 
vation of Atlantic Tunas (ICCAT), 
responsible for the management of 
