Microchemical provenancing of prey remains in cormorant pellets reveals the use of diverse foraging grounds

Johannes Oehm, Andreas Zitek, Bettina Thalinger, Anastassiya Tchaikovsky, Johanna Irrgeher, Thomas Prohaska, Michael Traugott

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung


Piscivorous birds in aquatic ecosystems exert predation pressure on fish populations. But the site-specific impact on fish populations, including stocked and commercially used fish species, remains disputed. One of the key questions for the management of piscivorous birds and fish is determining the origin of prey and thus which fish populations are targeted by the birds. We addressed this question by provenancing otoliths (earstones) of fish obtained from regurgitated pellets of piscivorous birds by otolith microchemistry analysis. We retrieved otoliths from regurgitated pellets of great cormorants (Phalacrocorax carbo sinensis) collected every 2 weeks for 2 years from breeding and roosting colonies at Chiemsee in Bavaria, Germany, and classified them according to family or species. We collected water samples from Chiemsee and potential surrounding foraging grounds. We measured the strontium (Sr) 87Sr/86Sr isotope ratio and Sr mass fraction of water and otoliths using (laser ablation) inductively coupled plasma-mass spectrometry. We assigned otoliths from regurgitated pellets to habitat clusters of origin by comparing the Sr isotopic and elemental composition of otoliths and waterbodies. In 36% of cormorant pellets collected at Chiemsee, prey was assigned to waterbodies distinct from Chiemsee. Furthermore, cormorants used different foraging sites during 1 day. Microchemical provenancing of prey remains can contribute to identifying foraging sites of piscivorous birds and to what extend the birds switched among foraging sites.
FachzeitschriftThe journal of wildlife management
Frühes Online-Datum8 Mai 2022
PublikationsstatusVeröffentlicht - Aug. 2022

Bibliographische Notiz

Funding Information:
We thank the Bavarian state agency for environment for providing digital maps of the study area and W. Suter, J. Trauttmansdorff, and the Bavarian state collection for providing otolith reference collections. We also thank C. Breitschopf, G. Fenkart, F. Feurstein, S. Leiter, L. Manzl, H. Mayr, T. Peham, L. Raso, C. Reichler, K. Staudacher, S. Steinmetz, D. Straube, J. Vorhauser, Z. Ye, and C. Zeisler for their assistance during field and laboratory work. We thank A. Retzmann and M. Schober for supporting the laser ablation inductively coupled plasma‐mass spectrometry analysis of otolith samples. Finally, we thank the anonymous reviewers for their helpful comments and suggestions on the manuscript. This study was funded by the Austrian Science Fund (number P24059) and grants from Hypo Tirol Bank, Swarovski, and Ph.D. scholarships (University of Innsbruck) for JO and BT, and a research scholarship for Austrian graduates of the University of Innsbruck awarded to BT. This work was also supported by a research project of the Austrian Competence Centre for Feed and Food Quality, Safety and Innovation, which is funded by the Austrian federal ministries BMK, BMDW and the Austrian provinces Lower Austria, Upper Austria and Vienna within the scope of COMET—Competence Centers for Excellent Technologies.

Publisher Copyright:
© 2022 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.

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