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Feeding habits of two pelagic fish thunnus albacares and Acanthocybium solandri from the galapagos marine reserve

Abstract:

This study analyzed the trophic niche of two pelagic species that inhabit the Galapagos Marine Reserve, with the aim of understanding the interactions between these predators and other species. From June to October of 2009, 238 stomachs of Thunnus albacares and 151 of Acanthocybium solandri were analyzed from 4 specific sites of the Archipelago. Prey diversity reached an asymptotic level at 11 and 100 stomachs respectively. A total of 28 prey were found in T. albacores, in which the Humboldt squid Dosidicus gigas (36.68%) was the numerically most represented, whereas 11 prey were found in A. solandri in which the flying fish Prognichthys tringa and D. gigas were the two main prey items representing 40% of the diet. In terms of weight and frequency of occurrence, the most important prey were the squids Histioteuthis heteropsis (8.75%) and D. gigas (63.41%) for T. albacares and Trachurus sp. (19.86%) and Prognichthys tringa (1.19%) for A. solandri. The index of relative importance (IIR) confirmed the importance of these items in the diet of both predators. The trophic breadth level classifies T. albacares as a specialist - and A. solandri as a generalist predator (Levin = 0.17 and 0.65, respectively). These results suggest important differences in feeding habits in the two apparently sympatric species, which allows them to minimize interactions between species and to maintain their sympatric presence in this region.