74 
Fishery Bulletin 110(1) 
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Total length (mm) 
Figure 2 
Total length-frequency distributions for (A) Scyliorhinus canicula and (B) Squa- 
lus blainuille collected off the Portuguese coast in 2006 and analyzed for diet 
composition, separated by sex. 
stomachs were used to characterize the diet of both S. 
canicula and S. blainville (Fig. 3). 
Scyliorhinus canicula exhibited a diverse diet, 
composed of 63 different taxa, belonging to eight 
taxonomical groups: Sipuncula, Annelida, Crustacea, 
Mollusca, Echinodermata, Urochordata, Chondrich- 
thyes, and Teleostei, as well as unidentified materials 
(Table 1). Crustaceans were by far the most abundant 
group in the diet of S. canicula, according to the nu- 
merical and occurrence indices, with values of 49.9% 
and 66.2%, respectively (Fig. 4). Within this group, 
the most important prey items were Pagurus spp. 
(including P. hernhardus, P. cuanensis, and Pagurus 
sp.) and non-identified Decapoda (Table 1). The sec- 
ond and third most abundant prey items in the diet 
of S. canicula according to the NI and OI were Tele- 
ostei and Annelida, respectively, although Teleostei 
contributed more significantly in weight, comprising 
almost 60% of the total weight of prey items in the 
stomach contents (Fig. 4A). From this last group, the 
pelagic fish Sardina pilchardus and Scomber scom- 
brus were the predominant species. The remaining 
prey groups — Sipuncula, Mollusca, Echinodermata, 
Urochordata, Chondrichthyes, and unidentified mate- 
rials — totaled less than 10% of the diet composition 
for all indices. 
Squalus blainville showed a less diverse diet, com- 
posed of 30 different prey item types, grouped into six 
taxonomical categories: Sipuncula, Annelida, Crustacea, 
Mollusca, Echinodermata, and Teleostei, as well as 
unidentified materials (Table 2). The most abundant 
prey items in the diet of S. blainville were crustaceans, 
according to the NI, OI, and GI (52%, 64%, and 44%, 
respectively). The most abundant crustacean species 
were Polybius henslowii and Pagurus spp., with the first 
species contributing more than half of the total crusta- 
cean prey items in weight (GI=28.5%). The second most 
abundant prey group for all indices was Teleostei (fol- 
lowed by unidentified materials), although with much 
lower contribution for the diet composition (Fig. 4B). 
In contrast to S. canicula where it was nearly 60% by 
weight, Teleostei comprised only about 30% by weight in 
S. blainville. In S. blainville , fish were heavily digested, 
and it was only possible to distinguish soleids from 
the remaining fish. Mollusca (mainly Cephalopoda and 
Gastropoda) played a more secondary role in the diet of 
S. blainville (Table 2), despite their higher proportions 
when compared to S. canicula (see also Fig. 4). 
Scyliorhinus canicula had a more diverse diet, feed- 
ing on a higher number of prey items (H'~ 2.61), where- 
as S. blainville had a slightly narrower diet breadth 
(iT=2.48). In contrast, the diet of S. blainville had high- 
