Mendez Macias et al.: Trophic ecology and ontogenetic shift in the diet of Mustelus lunulatus in the southeastern Pacific Ocean 
255 
Table 5 
Dietary overlap between size classes, dietary niche 
breadth (S A ), and trophic position (TP) in sicklefin smooth- 
hounds (Mustelus lunulatus) caught in the southeastern 
Pacific Ocean during November 2003-October 2004. The 
size classes are 60-90 cm in total length (TL, Size I), 
90-120 cm TL (Size II), and 120-150 cm TL (Size III). An 
asterisk (*) indicates high overlap. n=number of stomachs 
analyzed. 
Size 
class 
Size I 
(71=100) 
Size II 
(71=182) 
Size III 
(77=32) 
b a 
TP 
Size I 
_ 
0.02 
3.93 
Size II 
0.12 
- 
0.06 
3.60 
Size III 
0.31 
0.52* 
— 
0.13 
2.73 
range of 100-1000 km, highly omnivorous), intermediate 
mesopredators (maximum TL 150-300 cm, geographic 
range <10 km, high trophic position), or small mesopred¬ 
ators (maximum TL <100 cm, geographic range <10 km, 
generally not omnivorous). 
In accordance with these groupings, this study classified 
the sicklefin smoothhound as an intermediate mesopreda- 
tory shark (mean trophic position: 3.59 [SD 0.24]). This 
finding is consistent with the trophic position estimated 
by Cortes (1999) for the sicklefin smoothhound (3.9) and 
for other species of the genus Mustelus, for example, the 
brown smoothhound (3.6) and the gray smoothhound (M. 
californicus , 3.5). Our results indicate that the sicklefin 
smoothhound could be an important factor if there is a 
substantial change in the populations of other large shark 
species (Bornatowski et al., 2014b). 
In conclusion, the sicklefin smoothhound is an inter¬ 
mediate mesopredator that regulates the most abundant 
benthic crustacean populations along the coast of Ecuador. 
Generally, this species exhibits behavior and habitat segre¬ 
gation, and it is a selective predator that specializes in the 
consumption of highly abundant crustaceans off the coast 
of Ecuador. In this study, ontogenetic changes related to 
stage of maturity, size class, and time of year were observed 
in the diet of sicklefin smoothhounds. This study fills gaps 
in our knowledge of sharks in the waters of Ecuador and 
provides data for Ecuador’s national plan of action for the 
conservation and management of sharks (MICIP, 2006). 
Acknowledgments 
The authors thank the fishermen and storekeepers of 
Tarqui Beach in Manta. C. Estupinan-Montano thanks the 
Fundacion Alium Pacific, and F. Galvan-Magana thanks 
the Institute Politecnico Nacional programs Estlmu- 
los al Desempeno de los Investigadores and Comision de 
Operation y Fomento de Actividades Academicas. We thank 
I. Gambache and D. Edgar for editing our text for English. 
Literature cited 
Bohorquez-Herrera, J. 
2006. Aspectos biologicos y pesqueros de los elasmobranquios 
capturados en el Parque Nacional Natural Gorgona y su 
area de influencia entre 2004 y 2005. B.S. thesis, 104 p. 
Univ. de Bogota Jorge Tadeo Lozano, Bogota, Colombia. [In 
Spanish.] [Available from website.] 
Bornatowski, H., R. R. Braga, V. Abilhoa, and M. F. Correa. 
2014a. Feeding ecology and trophic comparions of six shark 
species in coastal ecosystem off southern Brazil. J. Fish 
Biol. 85:246-263. 
Bornatowski, H., A. F. Navia, R. R. Braga, V. Abilhoa, and M. F. 
M. Correa. 
2014b. Ecological importance of sharks and rays in a struc¬ 
tural foodweb analysis in southern Brazil. ICES J. Mar. Sci. 
71:1586-1592. 
Braga, R. R., H. Bornatowski, and J. R. Vitule. 
2012. Feeding ecology of fishes: an overview of worldwide 
publications. Rev. Fish Biol. Fish. 22:915-929. 
Brown, S. C., J. J. Bizarro, G. M. Cailliet, and D. A. Ebert. 
2012. Breaking with tradition: redefining measures for 
diet description with a case study of the Aleutian skate 
Bathyraja aleutica (Gilbert 1896). Environ. Biol. Fish. 
95:3-20. 
Chirichigno F., N., and J. Velez D. 
1998. Clave para identificar los peces marinos del Peru, 2 nd 
ed., 491 p. Publ. Espec. Inst. Mar Peru, Callao, Peru. [In 
Spanish.] [Available from website.] 
Clarke, M. R. 
1986. A handbook for identification of cephalopod beaks, 269 
p. Clarendon Press, Oxford, UK. 
Clarke, K. R., and R. N. Gorley. 
2006. PRIMER v6: user manual/tutorial, 18 p. PRIMER-E, 
Plymouth, UK. 
Clothier, C. R. 
1950. A key to some Southern California fishes based on 
vertebral characters. Calif. Dep. Fish Game, Fish Bull. 
79, 83 p. 
Colwell, R. K. 
2013. EstimateS: statistical estimation of species richness 
and shared species from samples. Vers. 9. User’s guide and 
application. [Available from website.] 
Compagno, L. J. V. 
1984. FAO species catalogue. Vol. 4, Sharks of the world: 
an annotated and illustrated catalogue of shark species 
known to date. Parts 1 and 2 (Hexanchiformes to Lamni- 
formes; Carcharhiniformes). FAO Fish. Synop. 125, vol. 4, 
655 p. FAO, Rome. 
Cortes, E. 
1999. Standardized diet composition and trophic levels of 
sharks. ICES J. Mar. Sci. 56:707-717. 
Del Rosario, J. B., and L. G. Abele. 
1976. Description of the male and new distribution records 
for Acanthocarpus delsolari Garth 1973 (Decapoda, Calap- 
pidae) from de Pacific coast of Panama. Crustaceana 
30:225-228. 
Eder, E. B., and M. N. Lewis. 
2005. Proximate composition and energetic value of demersal 
and pelagic prey species from the SW Atlantic Ocean. Mar. 
Ecol. Prog. Ser. 291:43-52. 
Ellis, J. R., M. G. Pawson, and S. E. Shackley. 
1996. The comparative feeding ecology on six species of 
shark and four species of ray (Elasmobranchii) in the 
north-east Atlantic. J. Mar. Biol. Assoc. U.K. 76:89-106. 
