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ORIGINAL ARTICLES

New insights on the trophic ecology of blue (Prionace glauca) and shortfin mako sharks (Isurus oxyrinchus) from the oceanic eastern South Pacific

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Pages 173-182 | Received 01 Dec 2016, Accepted 17 Oct 2017, Published online: 17 Jan 2018
 

ABSTRACT

The blue shark (Prionace glauca) and the shortfin mako shark (Isurus oxyrinchus) are two large and highly migratory sharks distributed in most oceans. Although they are often caught in the south Pacific Ocean long-line fisheries, their trophic ecology is poorly understood. Stable isotopes with Bayesian mixing and dependence concentration models were performed to determine the diet and trophic differences between the two species in the South-eastern Pacific Ocean. According to the mixing models, fishes are the most important prey of these sharks. Dolphin calves and remains were found in the stomachs of both species, which represents a novel finding in trophic ecology of South Pacific sharks. Intra-specific differences were found in P. glauca, but not in specimens of I. oxyrinchus. The two sharks showed a high degree of diet overlap (73%), primarily over mackerel and dolphin carcasses. Our results indicate that blue and shortfin mako sharks have a generalist feeding strategy in the eastern Pacific Ocean, with a strong preference for teleost fishes and also for dolphin carcasses. Therefore, trophic studies are useful to understand energy flow through the food web, and the trophic position of key species.

SUBJECT EDITOR:

Acknowledgements

The authors are grateful to Kaitlin Gallagher and Michael Hutson (Department of Ecology and Evolutionary Biology, University of Connecticut) for their valuable help in improving this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors .

Additional information

Funding

This work was supported by Subsecretaría de Pesca Chile (SUBPESCA) under grant ‘SRAM N° 2010-2013’: IFOP monitoring program, State of highly migratory resources, Fishing season 2010–2013.

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