78 
Fishery Bulletin 110(1) 
Table 2 
Stomach contents of Squalus blainville, according to the numeric (NI), occurrence (OI), and gravimetric (GI) indices. Between 
parentheses is the number of each prey item (NI), the number of nonempty stomachs where each prey item occurred (OI) and the 
weight (g) of each prey item (GI). Total number of stomachs=297; total number of stomachs with prey=233; total number of prey 
items=391; total weight of prey items=1420.58 g. 
Prey items 
NI 
OI 
GI 
Sipuncula 
0.77 (3) 
1.29 (3) 
0.94(13.32) 
Siphonosoma sp. 
0.26 (1) 
0.43 (1) 
0.08 (1.08) 
Sipuncula 
0.51 (2) 
0.86(2) 
0.86 (12.23) 
Annelida 
1.79 (7) 
3.00 (7) 
0.06 (0.81) 
Polychaeta 
1.79(7) 
3.00 (7) 
0.06 (0.81) 
Crustacea 
51.66 (202) 
63.52 (148) 
44.30 (629.29) 
Alpheus glaber 
0.26 (1) 
0.43 (1) 
0.08 (1.16) 
Anapagurus laevis 
0.26 (1) 
0.43 (1) 
0.10 (1.48) 
Pagurus bernhardus 
0.26 (1) 
0.43 (1) 
0.11 (1.49) 
Pagurus spp. 
2.81 (11) 
3.00 (7) 
1.32 (18.71) 
Paguridae 
0.77 (3) 
0.86(2) 
0.28(3.98) 
Polybius henslowii 
9.72(38) 
9.87 (23) 
28.50 (404.90) 
Portunidae 
3.84 (15) 
3.86(9) 
4.31 (61.25) 
Palaemonidae 
0.51 (2) 
0.43 (1) 
0.12 (1.74) 
Reptantia 
0.26 (1) 
0.43 (1) 
0.62 (8.81) 
Natantia 
3.58 (14) 
3.00(7) 
0.34 (4.84) 
Decapoda 
10.23 (40) 
14.59(34) 
5.02 (71.28) 
Eurydice affinis 
0.51 (2) 
0.86 (2) 
0.03 (0.36) 
Eurydice sp. 
0.26 (1) 
0.43 (1) 
0.01 (0.12) 
Isopoda 
0.77(3) 
1.29(3) 
0.03 (0.36) 
Crustacea 
17.65 (69) 
23.61 (55) 
3.44 (48.83) 
Mollusca 
11.25 (44) 
15.88(37) 
13.02(185.01) 
Calliostoma sp. 
0.26 (1) 
0.43 (1) 
0.01 (0.21) 
Gastropoda 
4.60 (18) 
6.44(15) 
1.17 (16.63) 
Haliotidae 
0.51 (2) 
0.43 (1) 
0.03(0.47) 
Bivalvia 
0.26 (1) 
0.43 (1) 
0.12 (1.69) 
Loligo vulgaris 
0.26 (1) 
0.43 (1) 
1.33(18.87) 
Sepia officinalis 
0.77(3) 
0.86(2) 
1.13 (16.02) 
Octopodidae 
0.77 (3) 
1.29 (3) 
4.03(57.30) 
Cephalopoda 
3.84 (15) 
5.58 (13) 
5.20(73.82) 
Echinodermata 
0.26(1) 
0.43 (1) 
0.07 (0.99) 
Holoturoidea 
0.26 (1) 
0.43 (1) 
0.07(0.99) 
Teleostei 
18.16 (71) 
30.04(70) 
30.51 (433.47) 
Soleidae 
0.26 (1) 
0.43 (1) 
1.56 (22.18) 
Teleostei 
17.90(79) 
29.61 (69) 
28.95(411.28) 
Unidentified material 
16.11 (63) 
26.61 (62) 
11.10 (157.61) 
that crustaceans and teleosts are the most important 
prey items in the diet of S. blainuille. 
This study also provided important information re- 
garding the potential for resource competition, given 
the high level of diet overlap between both species. 
Other than the fact that competition and predation 
are important features structuring the distribution 
of marine organisms, little is known about how com- 
petition and predation may influence the distribution 
of elasmobranch fishes (Papastamatiou et al., 2006). 
From a management point of view, it is important to 
determine the preferential prey items and feeding 
habitats of elasmobranchs in order to assess resource 
partitioning and competitive segregation among spe- 
cies that coexist in similar areas. In fact, given that 
both species were captured roughly at the same areas, 
competition should be more intense if both species use 
these habitats throughout their whole life-cycle. Olaso 
et al. (2005) observed in the Cantabrian Sea (Spain) a 
high diet similarity between two scyliorhinid sharks, 
whose depth range overlaps to some degree. 
Nevertheless, the potential for resource competition 
may be diminished by depth segregation, because S. 
blainville has been recognized to inhabit deeper water 
than S. canicula. The absence of larger S. blainville 
males in the sampled areas may also be an indica- 
