Inter-colony and inter-annual variation in discard use by albatross chicks revealed using isotopes and regurgitates

Kuepfer, A., Catry, P., Bearhop, S., Sherley, R. B., Bell, O., Newton, J. , Brickle, P., Arkhipkin, A. and Votier, S. C. (2023) Inter-colony and inter-annual variation in discard use by albatross chicks revealed using isotopes and regurgitates. Marine Biology, 170(4), 46. (doi: 10.1007/s00227-023-04191-7)

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Abstract

Effective marine ecosystem monitoring is critical for sustainable management. Monitoring seabird diets can convey important information on ecosystem health and seabird–fishery interactions. The diet of breeding black-browed albatross (Thalassarche melanophris) has previously been assessed using stomach content analysis (SCA) or stable isotope analysis (SIA), but not both methods together. Combining dietary sampling approaches reduces biases associated with using single methods. This study combines SCA and SIA to study the diet of black-browed albatross chicks, with a specific focus on fishery discard consumption, at two Falkland Islands colonies (New Island 51°43′S, 61°18′W and Steeple Jason Island 51°01′S, 61°13′W) during two consecutive breeding seasons (2019 and 2020). SCA provided high taxonomic resolution of short-term diet and priors for stable isotope mixing models, with multiple measures of dietary items (e.g. numeric frequency N%, frequency of occurrence FO%). By contrast, SIA of down feathers provided a single and more integrated dietary signal from throughout chick development. Although the two methods disagreed on the dominant prey group (SCA—crustacean; SIA—pelagic fish), the complementary information suggested a chick diet dominated by natural prey (SCA: 74%–93% [FO], 44%–98% [N]; SIA: minimum 87%–95% contribution). Nonetheless, SCA revealed that a high proportion of breeding adults do take discards. We detected consistent colony-specific diets in relation to prey species, but not in relation to higher discard use. Overall, discard consumption was highest in 2020, the year characterised by the poorest foraging conditions. Our results have implications for fisheries management and future dietary studies assessing discard use.

Item Type:Articles
Additional Information:This study had the support of the Fundação para a Ciência e a Tecnologia (FCT) I.P. through the strategic project UIDB/04292/2020, UIDP/04292/2020 and DivRestore/0012/2020 awarded to MARE and ISPA, and LA/P/0069/2020 granted to the Associate Laboratory ARNET. Further funding was provided by Fortuna Ltd., the Falkland Islands Government through the Environmental Studies Budget, as well as by the National Environmental Research Committee (NERC) through grants-in-kind (EK316-03/19, 2264.0420).
Keywords:Fishery discards, seabird diet, stomach content analysis, stable isotope analysis, Thalassarche melanophris.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Newton, Dr Jason
Authors: Kuepfer, A., Catry, P., Bearhop, S., Sherley, R. B., Bell, O., Newton, J., Brickle, P., Arkhipkin, A., and Votier, S. C.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Marine Biology
Publisher:Springer
ISSN:0025-3162
ISSN (Online):1432-1793
Published Online:16 March 2023
Copyright Holders:Copyright © 2023 The Authors
First Published:First published in Marine Biology 170(4): 46
Publisher Policy:Reproduced under a Creative Commons License

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