Diet of the bull shark, Carcharhinus leucas, and the tiger shark, Galeocerdo cuvier, in the eastern Pacific Ocean

Authors: COLOMBO ESTUPIÑÁN-MONTAÑO, JOSÉ F. ESTUPIÑÁN-ORTIZ, LUIS G. CEDEÑO-FIGUEROA, FELIPE GALVAN MAGAÑA, CARLOS J. POLO-SILVA

Abstract: This study presents information on the diet of two shark species, Carcharhinus leucas and Galeocerdo cuvier, that inhabit the southeastern Pacific Ocean. The stomachs were collected from October 2003 to July 2005 in Ecuador. Stomachs of 41 C. leucas and six G. cuvier were analyzed. According to the index of relative importance (%IRI), the most important prey for C. leucas were fishes: family Ophichthidae (13.41%), Tylosurus pacificus (9.79%), Katsuwonus pelamis (4.54%), and fish remains (44.81%). G. cuvier, for its part, consumed squids: Ancistrocheirus lesueuri (45.14%), Pholidoteuthis boschmaii (7.81%), and Octopoteuthis spp. (5.17%), as well as turtles: Caretta caretta (9.7%), Lepidochelys cf. kempii (5%), and turtle remains (16.5%). The results show that C. leucas (trophic level, I_TR; 4.32 $\pm$ 0.13) and G. cuvier (I_TR; 4.26 $\pm$ 0.09) are tertiary consumers, occupying high positions in the food chain, but also are generalist predators that feed on a variety of prey. The high frequency of sea turtles in the stomachs of G. cuvier (>300 cm) suggests that this shark species is an important predator of turtles, which are commonly found along the southeastern Pacific coasts.

Keywords: Top predator, feeding habits, trophic level, Ecuador, stomach contents

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