Lorien Pichegru
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.
Phone: +27 78 844 3863
Address: Coastal and Marine Research Institute, Nelson Mandela Metropolitan University, Port Elizabeth.
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.
Phone: +27 78 844 3863
Address: Coastal and Marine Research Institute, Nelson Mandela Metropolitan University, Port Elizabeth.
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management planning for African penguins. Satellite transmitters were deployed on 20 adults during the pre-moult foraging period from colonies on the west coast (Dassen Island, n=10) and south coast (Bird Island, Algoa Bay, n=10) of South Africa. Kernel density analyses were produced using nightly locations to create foraging range maps, which were compared to catches made by the small-pelagic fishery during September-December 2012.
Birds from the two colonies differed in their foraging strategies. Compared to penguins from Bird Island, those from Dassen Island spent more than six times the number of nights beyond the foraging range used during the breeding season (40 km from their colony). Birds from Dassen Island typically made long, looping trips more than 300 km away from the colony, and travelled further and at higher daily rates to foraging areas than individuals from Bird Island, feeding outside areas where fishing activity was highest. Kernel density analysis showed the foraging range of Dassen Island penguins was between Cape Columbine and the
central Agulhas Bank. Individuals from Bird Island continued to central place forage,
typically staying within 35 km of the colony. Penguins from Dassen Island that remained on
the west coast had to compete with higher levels of fishing pressure than penguins from Bird
Island. More than 70% of the fleet-wide, 2012 purse-seine catch occurred within the area where Dassen Island penguins spent 50% of their time. These colony-specific characteristics
suggest that management plans for African penguins need to be regionally targeted and incorporate larger foraging ranges during the pre-moult period for birds from western colonies. The larger foraging ranges and effort demonstrated by birds from the west coast suggest that a combination of the low relative fish abundance and higher commercial fishing pressure may force pre-moulting birds to seek food sources farther from the colony, putting them at higher risk of not surviving the annual moult. This project requires more years of data to ensure these foraging patterns are representative, and to more accurately provide
management suggestions directed to alleviate stress on African penguins for long-term protection of this endangered seabird.
African Penguins have short foraging ranges (10-50 km), and forage in dynamic coastal environments making them an ideal model for understanding how short-ranged top predators locate their prey. By modeling the sea-surface thermal habitat preferences, and the dive behavior in relation to thermoclines of African Penguins I assess how these short-ranged birds use ocean physical processes to increase the probability of locating their small pelagic prey. African Penguins breeding on Bird Island, Algoa Bay, were capable of utilizing temperature as a potential cue to foraging in three-dimensions. Penguins commuted east and south of their colony likely predicting the occurrence of cool nutrient rich waters from a periodic upwelling cell. Penguins departed in the early morning travelling towards these areas, maximizing the time they foraged during the day in cooler waters with a higher probability of containing prey patches. Penguins used a correlated random search strategy during foraging suggesting that these birds were continuously searching for prey, and it is therefore likely that penguins are limited by the patchy distribution of prey rather than a heterogeneous marine environment. When diving, penguins’ utilized thermoclines as either a potential cue to prey or by association, as their prey may be scattered around thermoclines. Penguins dived deeper foraging below the thermocline when the thermocline depth increased and also responded in their dive behaviour under different thermocline structures. For instance, when thermoclines were a diffuse barrier to nutrients and less likely to concentrate prey, birds dived deeper towards the benthos. Warm water intrusions into the bay from the Agulhas Current resulted in birds diving deeper in search of cooler bottom waters.
This research also demonstrates the dual utility of bio-loggers as a method for generating accurate, high-resolution oceanographic data. These data can be used in future studies, generating a cross disciplinary platform for research. This thesis augments our knowledge base of the African Penguin. African Penguins show flexibility in their foraging behaviour by adjusting their dive behaviour to subsurface thermal structures. Penguins also demonstrated foraging optimization by using temperature cues and behavioral switching to maximize the probability of locating prey patches on a fine temporal and spatial scale. ""