But even if these measures were taken, the long-term prognosis for the island’s colony of flightless birds is still gloomy. This is according to a new study by researchers from the University of Exeter, published in the Royal Society journal Biology Letters.
The study’s authors found that African penguin chick survival increased by just under 20 percent following a ban on catching sardines and anchovies in a 20km radius around the island between 2011 and 2013. Researchers conducted the study by monitoring how many chicks survived at hundreds of penguin nests on the island. They compared the survival rates for chicks in the years before the fishing ban was instituted, and while the ban was in place.
They found that, despite more healthy chicks surviving when fishing was banned, total numbers of the endangered birds on the island continued to decline. “Our study shows that small no-take (protected) zones can aid the survival of African penguin chicks. But ultimately commercial fishing controls must be combined with other management action if we are to reverse the dramatic decline of this charismatic species,” Dr Richard Sherley, from the University of Exeter, said in a media release.
Before Robben Island was settled by humans, penguins and other seabirds had the run of the small island. The flightless birds were hunted for food and exterminated by the early 19th century, but a colony was re-established in the mid-1980s.
African penguins – formerly called jackass penguins because their calls sound like braying donkeys – are listed as endangered on the International Union for Conservation of Nature’s Red Data List. They feed mostly on sardines and anchovies – fish also prized by commercial fishing operations – in waters around Cape Town.
Sherley said African penguins were highly “mobile,” meaning they travelled far to find prey. “Once they leave a protected area they are subject to outside pressures and dangers, including poor prey availability,” he said.
The authors of the study said penguins on Robben Island were exhibiting characteristics of seabirds suffering from a lack of food. “Seabirds will often respond to a scarcity of food by skipping or abandoning breeding, opting not to re-lay after losing clutches of eggs, or reducing the amount of food brought to the chicks leading to slow growth, poor chick condition and mortality through starvation.”
The authors said that, while there was more prey in the 20km Robben Island “protected zone”, other areas where the birds hunted for food were still open to commercial fishing. They said if the current fishing pressure exerted on sardine continued, there would not be sufficient food to allow the island’s penguin population to recover fully.
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