Because food availability affects African penguin breeding and survival rates, food shortages in South Africa and Namibia can’t maintain population equilibrium.
African penguin population declines have been attributed to food shortages, resulting from shifts in the distributions of prey species, competition with commercial purse-seine fisheries and environmental fluctuations. A decrease in foraging effort at St Croix Island and an increase in chick survival and chick condition at Robben Island following the establishment of 20 kilometer no-take zones provide some support for this theory.
In the early 2000s there was an eastward shift in sardine and anchovy, with the mature biomass of these species decreasing near the breeding islands north of Cape Town. The abundance of these prey species is known to influence breeding success, adult survival, and juvenile survival, all of which may often be too low off South Africa’s west coast to maintain population equilibrium.
In Namibia, where sardine and anchovy are virtually absent from the foraging ranges of breeding penguins, breeding birds feed principally on the energy-poor bearded goby Sufflogobius bibarbatus.
• Image | © Jean Wimmerlin, Some Rights Reserved, Unsplash
• Sources | (BirdLife International, 2016; Crawford, et al., 2006, 2011; Ludynia, Roux, Jones, Kemper, & Underhill, 2010; Pichegru, Grémillet, Crawford, & Ryan, 2010; Robinson, Butterworth, & Plagani, 2015; Sherley, et al., 2013; 2014, 2015; Weller, et al., 2014, 2016)