71 
Comparative feeding ecology 
of two elasmobranch species, Squaius blainville 
and Scyliorhinus canicula, off the coast of Portugal 
Filipe Mai tinho (contact author ) 1 
Catia Sa 
Joana Falcao 1 
Henrique Nogueira Cabral 2 
Miguel Angelo Fardal 1 
Email address for contact author: fmdm@cruc.pt 
1 CFE - Centre for Functional Ecology 
Department of Life Sciences 
University of Coimbra, Apartado 3046 
3001-401 Coimbra, Portugal 
2 Centro de Oceanografia 
Faculdade de Ciencias da Universidade de Lisboa, Campo Grande 
1749-016 Lisboa, Portugal 
Abstract — The small-spotted cat' 
shark ( Scyliorhinus canicula ) (Lin- 
naeus, 1758) and the longnose spurdog 
(Squaius blainville) (Risso, 1826) are 
two species occurring in the Euro- 
pean and western African continen- 
tal shelves with a wide geographical 
distribution. In this study, the diet of 
S. blainville and S. canicula off the 
Portuguese western Atlantic coast 
was investigated in 2006 by collect- 
ing monthly samples of these two spe- 
cies from local fishing vessels. In the 
stomachs of both species, crustaceans 
and teleosts were the dominant prey 
items, and molluscs, polychaetes, echi- 
noderms, and sipunculids were found 
in lower abundance. In S. canicula , 
urochordate and chondrichthyan spe- 
cies were also observed in stomachs 
and were classified as accidental prey 
items. Scyliorhinus canicula consumed 
a broader group of prey items than did 
S. blainville. A significant diet over- 
lap was observed, despite both spe- 
cies occupying different depth ranges 
over the continental shelf. Scyliorhi- 
nus canicula exhibited a consistency 
in diet composition among seasons, 
sexes, and maturity stages. Nonethe- 
less, for both adults and juveniles, 
an increase in relative abundance of 
teleosts in the diet was observed in 
the spring and summer. This study 
provides evidence of the importance 
of S. canicula and S. blainville as 
benthic and pelagic predators along 
the western Atlantic coast. 
Manuscript submitted 7 February 2011. 
Manuscript accepted 6 October 2011. 
Fish. Bull. 110:71-84 (2012). 
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. 
One of the main drawbacks in the 
assessment and management of elas- 
mobranchs is the lack of biological 
information and suitable fisheries 
data (Pawson and Vince, 1999; Hern- 
don et al., 2010). Being at the top 
of the marine food web, with mean 
trophic levels similar to marine 
mammals (Cortes, 1999; Domi et ah, 
2005), sharks are believed to play a 
significant role in marine ecosystems 
(Bowen, 1997). However, even for 
long and well-studied commercially 
important species, basic biological 
information (e.g., growth rates, age 
structure, reproductive potential, 
diet) that is essential for developing 
sound management strategies is still 
scarce (Stehmann et ah, 2009). 
In the Central Atlantic and Medi- 
terranean, the small-spotted catshark 
Scyliorhinus canicula (Linnaeus, 
1758) and the longnose spurdog 
( Squaius blainville) (Risso, 1826) are 
common demersal species (Pawson 
and Ellis, 2005; Froese and Pau- 
ly, 2010) and are direct targets for 
semipelagic longline and trammel 
fisheries (Coelho et ah, 2005). These 
species also constitute an important 
bycatch of trawl and artisanal coastal 
fisheries (Carbonell et al., 2003; Bae- 
ta et al., 2010). 
The distribution of S. canicula cov- 
ers a wide bathymetric range and 
spatial area in NE Atlantic Ocean 
(Norway and British Isles), south 
to Senegal and the Mediterranean 
Sea (Whitehead et al., 1986; Froese 
and Pauly, 2010). Scyliorhinus ca- 
nicula is an oviparous species with 
a high relative fecundity (Capape, 
1977) and is a broad generalist in 
its diet (Olaso et al., 2005). In the 
North Atlantic, this species displays 
diel vertical migrations: males oc- 
cupy deeper areas during the day 
and forage at night in shallow ar- 
eas, whereas females aggregate in 
shallow water caves during the day 
and forage at night in deeper waters 
(Sims et al., 2006). 
The longnose spurdog (S. blain- 
ville) (Risso, 1826) is an aplacental 
viviparous shark living in tropical 
and temperate waters, whose distri- 
bution range includes the Mediter- 
ranean, the Eastern Atlantic from 
the Bay of Biscay to South Africa, 
and the Western Atlantic from the 
United States to Argentina (Can- 
nizzaro et al., 1995; Froese and 
Pauly, 2010). It is a demersal spe- 
cies, inhabiting depths from 16 m 
to about 440 m and may reproduce 
throughout the year (Cannizzaro et 
al, 1995; Kousteni and Megalofonou, 
2011). References to the diet of this 
species are scarce, mainly restricted 
to Tunisian waters (Capape, 1975) 
