Percy FitzPatrick Institute, South Africa
My research focuses on seabirds foraging ecology and life history traits in relation with prey availability and local competition with industrial fisheries. I use animal-borne miniaturized recorders, such as GPS recorders combined with pressure sensors, cameras, etc, taped on adults breeding small chicks to determine the at-sea behaviour of several species of seabirds breeding in South Africa, all endemic to the region and threatened with extinction: the Cape gannet, the African penguin and the Cape cormorants. All three species have similar diet, small pelagic fish such as sardines and anchovies, yet different foraging and breeding strategies.
Through a decade of monitoring Cape gannets’ foraging behaviour and breeding success on the colony of Malgas Island, off the West Coast of South Africa, with the help of students and collaborators, we discovered the flexibility of these predators. Able to increase their energy and time spent at sea in search of their favourite prey, they will eventually turn to feed on the easy target of fishery discards if small pelagic fish are too scarce. Such diet apparently increased their winter survival and did not seem to have a long term effect on the body condition of adults, even after several years of feeding consistently on such a diet. However, their chicks have hardly a chance to fledge on this poor-energy food, constituted of fish bones, heads and guts. Therefore, we refuted the argument that providing discards for seabirds could compensate for the removal of their natural prey and highlighted the potential for high competition between seabirds and purse-seine fishing in the Benguela, to the detriment of the birds.
As part of a national experiment to determine if the drastic recent decreases in African penguin numbers, now Endangered, could be reduced by excluding fishing from penguin foraging areas, extensive monitoring take place on some African penguin colonies, some closed to fishing and some open, since 2008. Being a member of the Island Closure Task Team, part of the Small Pelagic Working Group from the Department of Agriculture, Forests and Fisheries, I’m in charge of monitoring the set of two islands in Algoa Bay, off Port Elizabeth. With the extensive help of many students and colleagues, as well as rangers from South African National Parks, we monitor their breeding success, chick growth, foraging behaviour, diet, survival and since recently, the distribution and abundance of their prey over time, in relation with purse-seine fishing activities. Shortly after fishing exclusion, breeding African penguins reduced their energy spent at sea in search for food, probably increasing their survival. However, the size of the fishing exclusion zone still remains insufficient to reverse the penguin population trends, with penguin chick growth and their breeding success remaining very low. While suggesting increasing the size of the fishing exclusion zone as a precautionary approach to prevent further loss in penguin numbers, we’re now concentrating on understanding penguin-prey interaction in relation with ocean-physical processes, in the hope to help in refining conservation strategies and optimize the use of the marine resources by fisheries and marine predators.