The Fish are the Key
Updated: Oct 19, 2019
Over the past century the African penguin population has been under threat from a multitude of human-induced actions. Whether it was direct poaching of the birds for food and use of their body fat, egg poaching for food items, stripping of the guano that they need for successful breeding, pollution of their environment, or climate change affecting the ocean they live in the human population has done everything possible to make life difficult for penguins. The most serious current threats to their future survival, however, comes in the form of a two pronged attack on their future. An overwhelming lack of suitable nesting locations due to the loss of all guano across the breeding range after a century of guano stripping for fertilizer has decimated their breeding success rate. Compounding the challenge, over-fishing and poaching of their badly needed food sources restricts the amount of food available both during breeding season and outside of it.
Studies have shown that juvenile African penguins are stuck foraging in places that the fish that they rely on no longer exist due to both commercial fishing and climate change. The challenge presents in two forms. First, the adult penguins are being forced to travel longer distances from the nesting colonies in order to find fish during chick rearing. Second, when the young penguins leave their colonies for the first time they must travel long distances, searching the ocean for signs that an area has plenty of fish. The indicators, especially chlorophyll, plankton and ocean temperatures, are no longer providing reliable information to the penguins for the location of the historically low schools of anchovies and sardines . This ecological trap (https://www.cell.com/current-biology/fulltext/S0960-9822(16)31536-6?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982216315366%3Fshowall%3Dtrue) is yet another in the long list of threats to the future existence of African penguins.
"These were once reliable cues for prey-rich waters, but climate change and industrial fishing have depleted forage fish stocks in this system," said Sherley.
"These signs can now lead them to places where these fish, the penguins' main prey, are scarce."
Researchers used satellites to track newly fledged African penguins from eight sites across their breeding range.
They found that many penguins were getting trapped in the Benguela Current Large Marine Ecosystem (BCLME), an area that stretches from southern Angola to Cape Point in South Africa's Western Cape.
The region has suffered from decades of overfishing and environmental changes, reducing the number of fish.
"The penguins still move to where the plankton are abundant, but the fish are no longer there," Sherley said.
Young penguins that wind up there often starve to death.
"Their breeding numbers are about 50 percent lower than they would be if they found their way to other waters, where the human impact has been less severe," said the study.
Scientists are considering the possibility of transporting young penguins to areas where food is more abundant.
African penguins are considered endangered by the International Union for Conservation of Nature (IUCN), with about 50,000 penguins remaining in Namibia and South Africa.
Food shortage is considered the main reason for their endangered status.
African penguins are "undergoing a very rapid population decline, probably as a result of commercial fisheries and shifts in prey populations," said the IUCN.
"This trend currently shows no sign of reversing, and immediate conservation action is required to prevent further declines."