252 
Fishery Bulletin 117(3) 
80 
-<>- Calappa saussurei 
-B- Crustacean remains 
-4- Squilla panamensis 
-O- Mursia spp. 
-jit* Lolliguncula (Loliolopsis) diomedeae 
Achelous iridescens 
lliacantha spp. 
-O- Euphylax robustus 
Figure S 
Diet composition of sicklefm smoothhounds (Mustelus lunulatus) caught in 
the southeastern Pacific Ocean between November 2003 and October 2004, 
by trimester of the year. The trimesters are November 2003-January 2004 
(Trimester I), February 2004-April 2004 (Trimester II), May 2004-July 2004 
(Trimester III), and August 2004-October 2004 (Trimester IV). 
examining other species of the genus Mustelus that indi¬ 
cate that their principal prey are crustaceans (Ellis 
et al., 1996; Rojas, 2006). The results of our study, how¬ 
ever, differ from the findings of Rojas (2000), Navia et al. 
(2006), and Navia et al. (2007), who reported that shrimps 
of the family Squillidae (e.g., Panama mantis shrimp and 
Squilla parva ) were the main prey of sicklefm smooth- 
hounds along the Pacific coast of Colombia. In contrast, 
the results of our study indicate that, although these 
shrimp species were present, they contributed little to 
the diet of sicklefm smoothhounds. This discrepancy can 
probably be attributed to the small number of stomachs 
(??=50, n- 42) and size classes (mainly 50-70 cm TL) ana¬ 
lyzed by Navia et al. (2006) and Navia et al. (2007), 
rather than to latitudinal variations that could affect the 
diversity and abundance of the main prey groups, 
because of the proximity of the localities studied. The 
distance between the location of this study (in Manta, 
Ecuador ) and the location of the studies by Navia et al 
(2006) and Navia et al. (2007) (in Buenaventura, Colom¬ 
bia) is approximately 760 km. 
Furthermore, Gomez et al (2003) and Bohorquez-Herrera 
(2006) conducted similar studies in areas close to the area 
studied by Navia et al. (2006) and Navia et al. (2007), and 
their results also differ from those obtained by Navia et al. 
(2006) and Navia et al. (2007). An example of latitudinal 
variation is the contrast in results obtained in the study 
by Moreno-Sanchez et al. (2012), who reported that in Baja 
California Sur, Mexico, sicklefm smoothhounds fed mostly 
on a squat lobster, Munida tenella, and the bigtooth rock 
crab ( Cancer amphioetus), 2 species that 
are distributed from Southern California 
in the United States to the Gulf of Cal¬ 
ifornia in Mexico (Nations, 1975; Hen- 
drickx, 2000). 
A likely explanation of the large pres¬ 
ence of A. iridescens in the stomachs of 
sicklefin smoothhounds in waters of 
Ecuador is the abundance of this species 
in the region, as found by Mora et al. 
(2010). That study demonstrated that 
the most abundant macroinvertebrates 
along the coast of Ecuador were A. irides¬ 
cens, followed by the arched swimming 
crab (C. arcuatus), dart squid, C. toxotes, 
and the pink shrimp (Farfantepenaeus 
brevirostris). These observations and 
results indicate that 1) sicklefin smooth¬ 
hounds feed primarily at depths between 
80 and 200 m (where there is the great¬ 
est abundance of A. iridescens, according 
to Mora et al., 2010) and 2) this species is 
a selective one, a trait that is associated 
with the abundance and availability of 
prey in the zones that it inhabits. 
The dietary analysis by sex revealed 
that both female and male sicklefin 
smoothhounds have a preference for A. 
iridescens, a result that, together with 
the high dietary overlap between the sexes (CA,=0.92), indi¬ 
cates that there is no sexual segregation in this species. 
This finding agrees with the dietary overlap (CA,=0.96) 
estimated by Moreno-Sanchez et al. (2012), despite the geo¬ 
graphical differences between the 2 studies. Nonetheless, 
these results must be interpreted with caution because 
they could represent “false positives,” as occurred in our 
study with the analysis of the values of trophic overlap by 
stage of maturity for separate sexes (Table 4) indicating 
that sicklefin smoothhounds present behavioral and hab¬ 
itat segregation (Wearmouth and Sims, 2008). However, 
juveniles of both sexes and female adults complement 
their principal diet (A. iridescens ) with coastal benthic 
prey that are typically associated with shallow waters and 
muddy-sandy seabeds, such as E. robustus (7-85 m) (Hen- 
drickx, 1995a) and Panama mantis shrimp (18-102 m) 
(Hendrickx, 1995b) and with coastal pelagic species, such 
as the dart squid (50-200 m) (Sanchez, 2003). 
The use of different feeding areas by juveniles of both 
sexes and female adults could be related to selection of 
breeding areas, abundance and availability of prey, devel¬ 
opment of hunting skills by juveniles, preferences for 
particular foraging zones pertaining to sex (McCord and 
Campana, 2003), size class, stage of maturity, and access 
to alternative sources of nutrition (e.g., pelagic prey; Eder 
and Lewis, 2005) related to specific stages of individual 
growth (Philips, 1969; Tytler and Calow, 1985). 
In contrast, male adult sicklefin smoothhounds prefer to 
complement their diet with the consumption of benthic 
coastal prey that exhibit a greater range of distribution, 
