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Feeding ecology of sympatric European shags Phalacrocorax aristotelis and great cormorants P. carbo in Iceland

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Abstract

The feeding ecology of the European shag (Phalacrocorax aristotelis) and the great cormorant (P. carbo) in Iceland was studied. These bird species may affect their marine environment, for instance, by predating on several commercially important fish species in coastal waters. The shag and cormorant diets were studied throughout the year in the period 1996–2000 by analysing the content of about 300 stomachs from each species. The shag relies heavily on sandeel (Ammodytes marinus) in the breeding season, whereas bull-rout (Myoxocephalus scorpius) and gadoids (Gadidae) become increasingly important in autumn and winter. The main food of the cormorant in all areas and seasons is the bull-rout. Depending on location and season, secondary food consists mainly of butterfish (Pholis gunnellus), gadoids and flatfishes (Pleuronectiformes). Similarity in diets of these two co-existing bird species was least in the breeding season when overlap in the birds’ distribution was greatest. The results suggest that predation by shags and cormorants could sometimes affect the stocks of the commercially important saithe (Pollachius virens) and plaice (Pleuronectes platessa) in Iceland.

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Acknowledgements

Thanks are extended to Prof. A. Gardarsson for access to unpublished data and reading of the manuscript, and G.A. Gudmundsson for comments on the manuscript and help with figures. A. Galan participated in data collection, and R. Olafsdottir, S. Gudmundsdottir, G. Haraldsdottir and S. Egilsdottir analysed stomach contents. L. Taylor commented on the manuscript, T.S. Gestsdottir assisted with data management, V. Bogason identified otoliths and E. Hjörleifsson provided information on fishery statistics. Thanks are also extended to the many hunters and fishermen, too numerous to mention, for collecting birds and two anonymous referees for improving the manuscript.

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  1. Marine Research Institute, Skulagata 4, 101, Reykjavik, Iceland

    Kristjan Lilliendahl & Jon Solmundsson

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  1. Kristjan Lilliendahl
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  2. Jon Solmundsson
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Correspondence to Kristjan Lilliendahl.

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Communicated by J.P. Thorpe, Port Erin

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Lilliendahl, K., Solmundsson, J. Feeding ecology of sympatric European shags Phalacrocorax aristotelis and great cormorants P. carbo in Iceland. Mar Biol 149, 979–990 (2006). https://doi.org/10.1007/s00227-006-0259-7

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