MEPS 367:223-232 (2008)  -  DOI: https://doi.org/10.3354/meps07621

Temporal and spatial variation in the diet of a marine top predator—links with commercial fisheries

Stephen C. Votier1,* Stuart Bearhop2, Ralph Fyfe3, Robert W. Furness4

1Marine Biology & Ecology Research Centre, School of Biological Sciences, University of Plymouth, Plymouth PL4 8AA, UK
2Centre for Ecology & Conservation, School of Biosciences, University of Exeter, Cornwall Campus, Penryn, Cornwall TR10 9EZ, UK
3School of Geography, University of Plymouth, Plymouth PL4 8AA, UK
4Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, UK

ABSTRACT: The huge quantities of waste produced by commercial fisheries worldwide attract large numbers of scavengers. Reducing this wasteful practice is desirable, but may have implications for marine ecosystems as scavengers will face a major shortfall in food. Predicting the impact of reduced discarding requires information on the strength of the link between scavengers and fisheries. We analysed sagittal otoliths regurgitated by great skuas Stercorarius skua over 5 yr from 8 different colonies in Shetland, UK, and over 18 yr from 1 of these sites, in relation to spatial and temporal variation in fisheries activity. The proportions of 2 demersal fish not normally available to skuas, haddock Melanogrammus aeglefinus and whiting Merlangius merlangus, are positively correlated with annual variation in discard estimates. The proportion of whiting at 8 colonies is positively correlated with spatial differences in fish biomass estimates, and blue whiting Micromesistus potassou are only eaten in colonies close to the continental shelf edge, where this species is fished. Non-breeding great skuas tend to eat smaller and significantly more variable discarded fish compared with breeders. Our results indicate that great skuas rely heavily on fishery discards and are also sensitive to spatial and temporal changes in fisheries activity. Differences between breeding status indicate that the non-breeding component of the population may respond differently to changing discard policy. The strength of the link between fisheries and scavengers appear to be species-specific, and testing the strength of these relationships should be an important avenue of future research to interpret the response of scavengers to changes in fisheries management.


KEY WORDS: Fisheries · Discards · Seabirds · Diet · Scavenger · Foraging


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Cite this article as: Votier SC, Bearhop S, Fyfe R, Furness RW (2008) Temporal and spatial variation in the diet of a marine top predator—links with commercial fisheries. Mar Ecol Prog Ser 367:223-232. https://doi.org/10.3354/meps07621

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