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Starving seabirds: unprofitable foraging and its fitness consequences in Cape gannets competing with fisheries in the Benguela upwelling ecosystem


Gremillet, D and Peron, C and Kato, A and Amelineau, F and Ropert-Coudert, Y and Ryan, PG and Pichegru, L, Starving seabirds: unprofitable foraging and its fitness consequences in Cape gannets competing with fisheries in the Benguela upwelling ecosystem, Marine Biology, 163, (2) Article 35. ISSN 0025-3162 (2016) [Refereed Article]

Copyright Statement

Copyright Springer-Verlag Berlin Heidelberg

DOI: doi:10.1007/s00227-015-2798-2


Fisheries are often accused of starving vulnerable seabirds, yet evidence for this claim is scarce. Foraging energetics may provide efficient, short-term indicators of the fitness status of seabirds competing with fisheries. We used this approach in Cape gannets (Morus capensis) from Malgas Island, South Africa, which feed primarily on small pelagic fish in the southern Benguela upwelling region, thereby competing with purse-seine fisheries. During their 20112014 breeding seasons, we determined body condition of breeding adult Cape gannets and measured their chick growth rates. In addition to these conventional fitness indices, we assessed the daily energy expenditure of breeding adults using a high-resolution time-energy budget derived from GPS-tracking and accelerometry data. For these same individuals, we also determined prey intake rates using stomach temperature recordings. We found that adult body condition and chick growth rates declined significantly during the study period. Crucially, most birds (73%) studied with electronic recorders spent more energy than they gained through foraging, and 8095% of their feeding dives were unsuccessful. Our results therefore point to unprofitable foraging in Cape gannets, with a longer-term fitness cost in terms of adult body condition and reproductive performance that corresponds to a local population decline. Based on this evidence, we advocate a revision of regional fishing quotas for small pelagic fish and discuss the possibility of an experimental cessation of purse-seine fishing activities off the west coast of South Africa. These measures are needed for the ecological and socio-economical persistence of the broader southern Benguela upwelling ecosystem.

Item Details

Item Type:Refereed Article
Keywords:seabird, foraging, fitness, gannets, fisheries, Benguela upwelling, West Coast, daily food intake, negative energy balance, positive energy balance, total allowable catch
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the biological sciences
UTAS Author:Peron, C (Dr Clara Peron)
ID Code:106574
Year Published:2016
Web of Science® Times Cited:29
Deposited By:Ecology and Biodiversity
Deposited On:2016-02-15
Last Modified:2018-04-05

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