Food limitation of seabirds in the Benguela ecosystem and management of their prey base

Authors

  • RJM Crawford Branch Oceans and Coasts, Department of Forestry, Fisheries and Environment, Cape Town, South Africa
  • WJ Sydeman Farallon Institute, Petaluma, CA, USA
  • DB Tom Ministry of Fisheries and Marine Resources, Lüderitz, Namibia
  • JA Thayer Farallon Institute, Petaluma, CA, USA
  • RB Sherley Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, UK
  • LJ Shannon Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
  • AM McInnes BirdLife South Africa, Cape Town, South Africa
  • AB Makhado Branch Oceans and Coasts, Department of Forestry, Fisheries and Environment, Cape Town, South Africa
  • C Hagen BirdLife South Africa, Cape Town, South Africa
  • RW Furness University of Glasgow, Glasgow, UK
  • T Carpenter-Kling BirdLife South Africa, Cape Town, South Africa and Institute for Coastal and Marine Research and Department of Zoology, Nelson Mandela University, Port Elizabeth, South Africa
  • C Saraux IPHC, CNRS, Université de Strasbourg, Strasbourg, France

Keywords:

Allee effects, Benguela seabirds, conservation thresholds, food limitation, Namibia, spatial management

Abstract

Four of seven seabirds that are endemic to the Benguela ecosystem (African Penguin Spheniscus demersus, Cape Gannet Morus capensis, Cape Cormorant Phalacrocorax capensis, Bank Cormorant P. neglectus) compete with fisheries for prey and have an IUCN classification of Endangered. Prey depletion and food resource limitations have been major drivers of recent large population decreases of each of these species. As populations decrease, colony sizes also dwindle rendering them susceptible to Allee effects and higher probabilities of extinction. Therefore, it is necessary to maintain colonies at sizes that minimise their probability of extinction. Means to ensure an adequate availability of food to achieve this goal include closing important seabird foraging areas (often adjacent to key colonies) to relevant fishing, implementing ecosystem thresholds below which such fishing is disallowed (which are also expected to benefit forage resources) and, should there be an altered distribution of prey, attempting to establish seabird colonies close to the new location of forage resources.

Published

2022-02-02

Issue

Section

Section A: Research articles