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Feeding ecology and consumption rate of broadbill swordfish (Xiphias gladius) in Ecuadorian waters

Abstract:

The feeding ecology and consumption rate of the broadbill swordfish (SWO, Xiphias gladius) from Ecuadorian waters were assessed by stomach content analysis of 256 individuals ranging between 91 and 291 cm in straight fork length (FL). Based on the alimentary index (%AI), the jumbo squid (Dosidicus gigas) was the most important prey species (58.93%AI), followed by bullet and frigate tunas (Auxis spp.) (17.94%AI). Permutational multivariate analysis of variance (PERMANOVA) detected one size-related shift in feeding habits to occur at FL ~ 190 cm, whereas no spatial variations in diet composition were observed. Similarity percentages (SIMPER) analysis revealed that the diet of small SWO (≤ 140 cm FL) and medium SWO (140–190 cm FL) was mainly characterized by Dosidicus gigas (contributing to 50.77 and 66.82% of the similarities, respectively) and Auxis spp. (18.14 and 17.23%, respectively); Auxis spp. and Thysanoteuthis rhombus, however, were the greatest contributors to the similarity in large SWO (≥ 190 cm FL) (47.87 and 22.06%, respectively). The daily meal was estimated to be 468.03–676.78 g day −1 , which corresponded to a daily ration of 1.63–8.24% body mass (BM, in g) day −1 . The results of this study indicate that the SWO is a mesopelagic predator that plays an important role in structuring the pelagic ecosystem of the Ecuadorian Pacific Ocean.