Surviving off junk: low-energy prey dominates the diet of African penguins Spheniscus demersus at Mercury Island, Namibia, between 1996 and 2009

  • K Ludynia
  • J-P Roux
  • R Jones
  • J Kemper
  • LG Underhill

Abstract

The diet of African penguins Spheniscus demersus in Namibia consisted mainly of sardine Sardinops in the 1950s. Since the collapse of pelagic fish stocks in the 1970s, birds fed mainly on bearded (pelagic) goby Sufflogobius bibarbatus, a low-energy prey species. We present diet data for African penguins breeding at Mercury Island, the largest colony for this species in Namibia, between 1996 and 2009. Bearded goby was the main prey item throughout the study period, both in terms of frequency of occurrence (67.8%; SD 31.2) and in terms of mass (59.2%; SD 31.5). Diet composition varied throughout the year as well as between years; birds occasionally fed on a variety of fish species other than bearded goby. In Namibia, poor prey abundance is considered as a major factor contributing to the decline of penguin numbers after the collapse of the sardine stocks. However, bearded goby appears to be relatively abundant along Namibia’s southern coast and low prey quality rather than low abundance appears to be a key factor influencing population dynamics of African penguins and other marine top predators in southern Namibia.

Keywords: African penguin, bearded (pelagic) goby, Benguela upwelling system, diet, Mercury Island, prey quality, Spheniscus demersus, Sufflogobius bibarbatus

African Journal of Marine Science 2010, 32(3): 563–572

Author Biographies

K Ludynia
Animal Demography Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Rondebosch 7701, South Africa
J-P Roux
Animal Demography Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Rondebosch 7701, South Africa; Ministry of Fisheries and Marine Resources, Lüderitz Marine Research, PO Box 394, Lüderitz, Namibia
R Jones
Ministry of Fisheries and Marine Resources, Lüderitz Marine Research, PO Box 394, Lüderitz, Namibia
J Kemper
Ministry of Fisheries and Marine Resources, Lüderitz Marine Research, PO Box 394, Lüderitz, Namibia; African Penguin Conservation Project, PO Box 583, Lüderitz, Namibia
LG Underhill
Animal Demography Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Rondebosch 7701, South Africa
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X