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Marine Ecology Progress Series

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MEPS 661:187-201 (2021)  -  DOI:

Influence of fisheries on the spatio-temporal feeding ecology of gulls along the western Iberian coast

J. G. Calado1,2,3,*,#, S. N. Veríssimo3,#, V. H. Paiva3, R. Ramos4, P. T. Vaz3, D. Matos3, J. Pereira3, C. Lopes3, N. Oliveira5, A. Quaresma3,6, F. R. Ceia3, A. Velando2, J. A. Ramos3

1University of Minho, CBMA - Molecular and Environmental Biology Centre, Campus de Gualtar, 4710-057 Braga, Portugal
2Animal Ecology Group, Lab 97, Torre CACTI, Campus As Lagoas, Universidade de Vigo, Spain
3University of Coimbra, MARE - Marine and Environmental Sciences Centre, Department of Life Sciences, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
4Biodiversity Research Institute (IRBio) and Department of Evolutionary Biology, Ecology and Environmental Sciences (BEECA), Faculty of Biology, Universitat de Barcelona, Av Diagonal 643, Barcelona 08028, Spain
5SPEA - Sociedade Portuguesa para o Estudo das Aves, Av. Columbano Bordalo Pinheiro, 87, 3º andar, 1070-062 Lisboa, Portugal
6Parque Natural da Ria Formosa, 8700-221 Olhão, Portugal
*Corresponding author:
#These authors contributed equally to this work

ABSTRACT: Gulls are highly opportunistic seabirds, and the exploitation of fishery discards has led to many population increases worldwide. We investigated the importance of fish in the diet of yellow-legged Larus michahellis and Audouin’s gulls L. audouinii and assessed the influence of fishery discards on their feeding ecology. We collected pellets from 4 islands along the western Iberian coast during pre-breeding, breeding, and post-breeding seasons from 2014 to 2018. Stable isotopes (from adult blood, and chick and adult feathers) were used to investigate spatial, seasonal, and inter-annual differences in their feeding ecology. We used pellet, stable isotope (δ15N, δ13C, and δ34S), and biochemical (triglycerides, uric acid, total protein, and carotenoids in adult plasma) analyses to investigate their relationships with fish landings across the annual cycle. Results revealed that the fish species consumed by gulls matched those landed by local fisheries on all study islands, and there was a positive association of pelagic and demersal fish diets with fish landing quantities for 2 islands. δ34S values suggest different self-feeding and chick-provisioning strategies in relation to fisheries. δ15N values exhibited strong negative correlations with fish landings, and triglycerides were positively correlated with pelagic but not with demersal fish landing quantities, suggesting that gulls fed more on lower trophic level and higher energetic content pelagic fish than on demersal fish. Overall, our results based on several techniques suggest that gull feeding ecology was linked to fishery discards, which in view of the new EU landing obligation may have major implications for both gull populations across Europe.

KEY WORDS: Larus michahellis · Larus audouinii · Pellets · Stable isotopes · Plasma biochemistry · Fishery discards

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Cite this article as: Calado JG, Veríssimo SN, Paiva VH, Ramos R and others (2021) Influence of fisheries on the spatio-temporal feeding ecology of gulls along the western Iberian coast. Mar Ecol Prog Ser 661:187-201.

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