Marine Biology

, 163:35 | Cite as

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

  • David GrémilletEmail author
  • Clara Péron
  • Akiko Kato
  • Françoise Amélineau
  • Yan Ropert-Coudert
  • Peter G. Ryan
  • Lorien Pichegru
Original paper


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 2011–2014 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 80–95 % 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.


West Coast Daily Food Intake Negative Energy Balance Positive Energy Balance Total Allowable Catch 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This study was funded by the FitzPatrick Institute, DST-NRF Centre of Excellence at the University of Cape Town (South Africa) and the Centre National de la Recherche Scientifique (CEFE-CNRS, UMR5175 Montpellier, France). We warmly thank Pierre Nel and SANParks for accommodation and logistical support. We are also particularly grateful to Lea Cohen, Itai Mukutyu, Emilie Tew Kai, Timothée Cook, Bruce Dyer, Rabi’a Ryklief, Leshia Upfold and Plaxedes Vimbai-Rukuni for their help in the field, to Jonathan Green for essential input on seabird energetics and to Carl van der Lingen for comments upon an initial draft version.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical standard

All experiments were performed under permits from South African National Parks with respect to animal ethics (No. CRC/2015/001—2002), and all protocols were validated by the French Direction des Services Vétérinaires (Permit No. 34-369).


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • David Grémillet
    • 1
    • 2
    Email author
  • Clara Péron
    • 3
  • Akiko Kato
    • 4
    • 5
  • Françoise Amélineau
    • 1
  • Yan Ropert-Coudert
    • 4
  • Peter G. Ryan
    • 2
  • Lorien Pichegru
    • 6
  1. 1.Centre d’Ecologie Fonctionnelle et Evolutive, UMR 5175CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHEMontpellierFrance
  2. 2.Percy FitzPatrick Institute, DST-NRF Centre of ExcellenceUniversity of Cape TownRondeboschSouth Africa
  3. 3.Institute for Marine and Antarctic StudiesUniversity of Tasmania and Australian Antarctic DivisionKingstonAustralia
  4. 4.UMR7372CEBCVilliers en BoisFrance
  5. 5.IPHC, UMR7178CNRSStrasbourgFrance
  6. 6.Coastal Marine Research InstituteNelson Mandela Metropolitan UniversityPort ElizabethSouth Africa

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