Gonzalez-Pestana et al.: Trophic ecology of Sphyrna zygaena off northern Peru 
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Teleosts 
M. den tat a 
D. gigas 
D. gahi 
G. antarcticus 
A. dux 
A. lesueurii 
Other prey 
Size classes 
Figure 3 
Index of relative importance expressed as a percentage (%IRI) for the 4 size classes (I: 53-70 
cm TL, II; 71-100 cm TL, III: 101-190 cm TL, IV: 191-294 cm TL) of smooth hammerhead 
(Sphyrna zygaena) collected off northern Peru from December 2012 through June 2015. The 
numbers above the bars indicate the sample size (number of stomachs collected) for each 
size class. 
served in other studies of smooth hammerhead (Bolafio 
Martinez, 2009; Ochoa Dias, 2009). 
Foraging grounds and predator-prey relations 
Populations of jumbo flying squid can impact the dy¬ 
namics of marine ecosystems, owing in part to the 
rapid growth characteristics of the species (e.g., rapid 
growth rate, short life span) (Gilly et al., 2006). For 
example, an increase in the jumbo flying squid popu¬ 
lation resulted in population declines of Chilean hake 
(Merluccius gayi ) and Pacific hake (.Merluccius produc- 
ius), and affected the catches of commercial fisheries 
for these species along Chile and California (Aranci- 
bia and Heir a 4 ; Jereb and Roper, 2010). In the eastern 
Pacific Ocean, this study, and previous studies, have 
identified smooth hammerhead as an important preda¬ 
tor of jumbo flying squid and one of the main predators 
of eephalopods in the eastern Pacific Ocean (Galvan- 
4 Arancibia, H., and S. Neira. 2006. Assessing the potential 
role of predation by jumbo squid {Dosidicus gigas) and fishing 
on small pelagics (common sardine Strangomera bentincki 
and anchovy Engraulis ringens ) and common hake ( Merluc¬ 
cius gayi) in central Chile, 33-39°S. In The role of squid in 
open oceans ecosystems. Report of a GLGBEC-CLIOTOP/ 
PFRP workshop, 16-17 November 2006, Honolulu, HI, USA 
(R. J. Olson and J. W. Young, eds.), p. 68-70. GLQBEC Rep. 
24. [Available from website.] 
Magana et al., 1989; Castaneda and Sandoval, 2004; 
Estupinan-Montano and Cedefio-Figueroa, 2005; Bola- 
ho Martinez, 2009; Ochoa-Diaz, 2009; Galvan-Magana 
et al., 2013). It is likely, therefore, that the smooth 
hammerhead plays an important role as a biological 
control of eephalopods, and, as a result, has important 
direct and indirect effects on the viability of multiple 
fisheries. Furthermore, the high abundance of jumbo 
flying squid (Nesis, 1983; Nigmatullin et al., 2001; Ar- 
giielles ef al., 2008) and massive smooth hammerhead 
fishery landings in northern Peru (Bonfil, 1994; Fischer 
et al., 2012; Gonzalez-Pestana et al., 2016) make clear 
that this ocean region represents an important feed¬ 
ing area for smooth hammerhead in the eastern Pacific 
Ocean. This study contributes to the basic understand¬ 
ing of the trophic ecology of smooth hammerhead and 
provides information that can also contribute to the 
design and implementation of national or regional con¬ 
servation plans for the smooth hammerhead. 
Acknowledgments 
The authors thank the following institutions who funded 
this study: Fondo para la Innovacion, la Ciencia y la 
Tecnologla (PIBA-369-2014), Rufford Foundation, PADI 
Foundation, Whitney Fund for Nature, and Darwin Ini¬ 
tiative. They thank A. Jimenez, S. Pingo, J. Xavier, S. 
