Climate Change, Over-fishing Threatening African Penguins – Scientists
Climate change is directly causing potentially catastrophic falls in the African penguin population in the crucial Benguela ecosystem, say scientists in the UK and South Africa.
A team led by Dr. Richard Sherley, from the University of Exeter’s Environment and Sustainability Institute, tagged 54 juvenile African penguins from eight colonies and tracked them across their breeding distribution.
Sherley said overfishing, combined with environmental changes off western South Africa, is dramatically reducing populations of fish eaten by penguins in the regions.
Changes in both the temperature and salinity of the waters in the Benguela ecosystem is causing fish to move east. As a result, the young penguins are hunting for food in the wrong places.
“The Benguela upwelling ecosystem is one of the world’s most productive ecosystems, but it’s also very heavily influenced by human actions,” Sherley told Reuters at the university’s Penryn campus.
“There’s evidence of climate change induced shifts in the Benguela which have caused species to shift eastwards and of strong impacts of fishing in parts of the Benguela. In Namibia particularly fish stocks, stocks of sardine, have collapsed.”
Juvenile African penguins seek out areas of low sea temperatures and high chlorophyll-a, which indicates the presence of plankton and therefore the fish, such as sardines and anchovies, which feed on it.
“When they (juvenile penguins) go to sea for the first time, they’re not helped by their parents and don’t have any knowledge of where they might find food. All they can do is follow cues that they’ve evolved to detect. So they end up where there’s no food and as a consequence, the first year survival for African penguins is very low,” said Sherley.
Sherley says environmental degradation causes maladaptive habitat selection so that cues which used to work for a species now put them in danger.
“They travel over thousands of kilometres to get to these particular locations. When they get there they’re not finding the food that they need. The human impacts have broken the system in a certain way, so they’re getting stuck in what’s known as an ecological trap.”
The African penguin, once known as the jackass penguin, is listed as endangered by the International Union for Conservation of Nature. The situation in the Benguela ecosystem is worsening their plight.
“Our population modelling suggests the Western Cape population is about 50 per cent the size that it would be if this trap wasn’t operating; the African penguin is endangered. It’s declined by more than 50 per cent over the last three generations, so around 30 years. The Western Cape population which used to be the stronghold has declined by about 80 per cent in the last 11 or 12 years.”
Sherley believes that fishing should be suspended when prey biomass drops below certain levels and says major conservation action is required to save the bird.
The research was carried out in conjunction with the University of Cape Town and published in the journal Current Biology.