Winners and losers – responses to recent environmental change by South African seabirds that compete with purse-seine fisheries for food
Abstract
There were recent changes in the distributions of the main prey of four seabirds off South Africa, with sardine Sardinops sagax and anchovy Engraulis encrasicolus shifting from South Africa's north-west coast towards the south-east. This contributed to numbers of African Penguins Spheniscus demersus and Cape Cormorants Phalacrocorax capensis breeding in South Africa decreasing by more than 50%. By contrast, numbers of Cape Gannets Morus capensis and Swift (Crested) Terns Thalasseus bergii increased. The success of the gannet and the tern in the face of recent change is attributable to a rapid increase in South Africa's eastern colony of gannets, aided by high survival of adult birds and perhaps by immigration of first-time breeders from decreasing western colonies, and a probable high production of Swift Terns. The gannet has an extensive foraging range and the tern is nomadic between breeding localities, which gives these species greater flexibility than the other two to adapt to large changes in the distributions of their prey. Additionally, the gannet is able to supplement its diet with fishery discards. A lesser mobility of the African Penguin and the Cape Cormorant rendered them susceptible to a reduced local availability of prey and both species suffered high adult mortality in the last decade.
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The African penguin is classified as Endangered following a decrease in the global population of more than 70% between 2001 and 2013.
“The African penguin Spheniscus demersus is ‘Endangered’ following a decrease in the global population of >70% between 2001 and 2013 [3], [4].”
From Hand-Rearing, Release and Survival of African Penguin Chicks Abandoned Before Independence by Moulting Parents (2014) · cites this paper as [4]
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Self-citation
- Authors
- Crawford, R. J., Makhado, A. B., Waller, L. J., & Whittington, P. A.
- Affiliations
- University of Cape Town (ZA)
- CapeNature (ZA)
- Nelson Mandela University (ZA)
- Corresponding author
- Crawford, Robert JM
- Venue
- Ostrich
- Published
- 2014-05-04
- Volume
- 85
- Issue
- 2
- Pages
- 111-117
- ISSN
- 0030-6525 (ISSN-L)
- 1727-947X
- OpenAlex
- W1974969877
- Cited by
- 39
- References
- 47
- Citations by year
- 2023: 3 · 2022: 4 · 2021: 4 · 2020: 3 · 2019: 7 · 2018: 4 · 2017: 3 · 2016: 5 · 2015: 2 · 2014: 4
- FWCI
- 4.06
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Ostrich (publishedVersion)
- Nelson Mandela University Research Repository (submittedVersion)
- Funders
- National Research Foundation
- Nelson Mandela Metropolitan University
- Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
- Nelson Mandela University
- Topics
- Physical Sciences › Environmental Science › Ecology › Avian ecology and behavior
- Physical Sciences › Environmental Science › Ecology › Marine animal studies overview
- Physical Sciences › Environmental Science › Global and Planetary Change › Marine and fisheries research
- Keywords
- sardine, anchovy, African penguin, Cape cormorant, Cape gannet, purse seine fishing, fish discards, seabird colonies, adult mortality, foraging range, nomadism
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
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