BirdLife: The Magazine Jan-Mar 2018 - Page 29

gannets nosedive Christina Hagen, Marine Conservationist - BirdLife South Africa he word “gannet” is synonymous with gluttony - but lack of food is becoming a serious problem for the Cape Gannet Morus capensis. The global population of this seabird, endemic to South Africa and Namibia, has dropped by more than half between 1956 and 2015 – resulting it its uplisting from Vulnerable to Endangered in this year’s Red List update. The main cause is lack of food. In Namibia, overfishing of the gannets’ preferred prey, sardine and anchovy, caused the almost complete collapse of fish stocks in the 1960s, and they have yet to recover. In South Africa, the fish stocks have shifted from the west coast to the south and east. To make up for these shortages, Cape Gannets congregate behind fishing vessels in search of Cape hake and other sea floor-dwelling fish. The boats process their catch as they go, dumping the heads, tails and guts of the filleted fish overboard. But while there is evidence that eating hake discards has helped adult Cape Gannets maintain body weight and condition when they cannot find their natural food, it has proved to be a double-edged sword. Until very recently, thousands of seabirds, including gannets, were being accidentally tangled and drowned in the fishing gear of these vessels. Thanks to the work of the Albatross Task Force (see page 30), these deaths have been dramatically reduced. However, because of their unique feeding style, some gannets still die from plunging vertically into the net. Another disadvantage of the hake discards is their energy content. Sardine and anchovy are full of omega-3 fatty acids that we humans are always being urged to eat. Hake discards are not. While a junk food diet can sustain the adults, research has shown that chicks fed on hake discards grow more slowly and have a lower chance of survival than those fed on a more natural diet. And it’s not just sub-standard food the juveniles have to worry about. On Malgas Island in South Africa, food scarcity means that both parents are often forced to forage simultaneously, leaving the young unguarded and exposed to attacks from the Great White Pelican Pelecanus onocrotalus. To add to their struggle, Cape Gannets also face threats from oil spills in an increasingly active shipping region at the southern tip of Africa. Louis Lotter T 29