Weekend Argus (Saturday Edition)
Gannets at risk of becoming endangered
FOR seabird conservationists, it’s the ultimate irony: a plunge-diving species famous for its greed is starving because of commercial overfishing and climate change.
The word “gannet” is synonymous with gluttony but a lack of nutritious food is edging the blue-eyed Cape gannet, which breeds only in South Africa and Namibia, close to extinction.
The large, distinctive species has been up-listed from vulnerable to endangered, largely because of population declines of 50% since the 1950s, caused by depleted fish stocks.
This is according to the latest update on the conservation status of the world’s birds by BirdLife International for the International Union for Conservation of Nature Red List of Threatened Species, which was released last week.
Overfishing of the Cape gannet’s preferred prey in Namibia – sardine and anchovy – caused the almost complete collapse of fish stocks in the 1960s, it says.
“They have yet to recover.”
For reasons that are unclear, in South Africa fish stocks have shifted from the west coast to the south and east. “The result is Cape gannets going hungry.”
Christina Hagen, a seabird scientist at BirdLife SA, said to make up for the lack of food, the birds started congregating behind hake fishing vessels.
But this not only increases the risk of accidental tangling and drowning in fishing gear – the discarded off-cuts are low in nutrients.
This isn’t a problem for the adults, but chicks fed on this “junk food” grow slowly and have a lower chance of survival than if fed on a natural diet.
“Sardine and anchovy are full of omega-3 fatty acids that humans are always being urged to eat.” Hake discards are not.
“The chicks need that fatty fish to grow and to survive. Studies have shown the chicks fed on these discards don’t do as well.”
BirdLife International says that until very recently, thousands of seabirds were being accidentally tangled and drowned in the fishing gear of vessels.
But the pioneering work of the Albatross Task Force has cut these deaths by up to 80% in some fisheries. “However, because of their unique feeding style, some gannets still die from plunging vertically into the nets, unable to avoid the allure of the fish so tantalisingly close by.”
For Hagen, it’s how fast the species is declining that is the real worry.
“We’re losing gannets very quickly. In general, the amount of fish taken out is not problematic, but it’s where and when the fish are removed. We need to take into account all the seabirds and other predators who eat fish, to make sure there’s enough left of them in the areas where they need it.
“The fact some of our seabird species are struggling means some- thing is wrong in the ocean. It’s up to us to try help make it better, not only for the seabirds, but also for humans, because we depend on the environment as a source of food and livelihoods.”
The regional breeding population of the Cape gannet, although numbering 240 000 mature individuals, she says, is confined to only three colonies in South Africa: Lamberts Bay, Malgas Island in Saldanha Bay, and Bird Island in Algoa Bay, which are “vulnerable to catastrophic events”.
There are numerous threats facing the species, including how rising temperatures may hit the chicks as the birds breed in summer, says Hagen.
Predation by seals is another big problem. “Seals can take out several birds in a day. Individual seals are being culled when they are seen killing a gannet because it’s a major threat if seals take out half the gannets produced in a year,” she says.
On Malgas Island, food scarcity means both parents are often forced to search simultaneously, leaving the chicks exposed to attacks from the great white pelican.
Gannets also face threats from oil spills.