Conserving Benguela endemic seabirds
All three seabirds endemic to the Benguela upwelling ecosystem that rely on anchovies and sardines are threatened by local reductions in the availability of their preferred prey. Small pelagic fish abundance has decreased off the southern African west coast, where fishing effort is concentrated, and most seabird breeding islands are located. As a result, it is crucial to understand the foraging behaviour of breeding seabirds and how their populations respond to changes in fish abundance and distribution.
The lack of spatial management of the fishery for small pelagic fish has resulted in local over-exploitation of sardines and anchovy. Throughout the last decade, the small pelagics fishery has failed to meet its quota almost every year, indicating a paucity of these fish. African Penguins Spheniscus demersus, Cape Cormorants Phala-crocorax capensis and Cape Gannets Morus capensis all depend largely on these same fish, and all three species are now listed as Endangered. Understanding the drivers behind such population changes is essential to mitigate these declines. This is a large, multi-faceted programme with key participants including Pierre Pistorius, Lorien Pichegru and Maëlle Connan (NMU), David Grémillet (CNRS Montpellier), former post-docs Tim Cook (Paris) and Richard Sherley (Bristol), collaborators at BLSA (Alistair McInnes, Christina Hagen) and DEA (Azwianewi Makhado and Rob Crawford), as well as several post-doctoral students.
Activities in 2020
- The experimental closure of commercial fishing for small pelagic fish around key penguin breeding islands continued in 2020, but no penguin data could be collected at either island due to strict COVID-19 lockdowns during the peak breeding season. Before the lockdown, only 1 500 breeding pairs were estimated on St Croix Island, which up until 2016 used to host 6 500–8 500 pairs.
- Strong arguments were made to the Small Pelagic Working Group and the Minister of the Department of Environment, Forestry and Fisheries (DEFF), Barbara Creecy, to urgently stop purse-seine fishing within 20 km of six penguin colonies, but no action was taken.
- A collaboration between NMU, BirdLife South Africa and the CNRS in France was established to investigate the factors driving the decline of the St Croix Island penguin colony since 2016, including the noise associated with maritime traffic, and its increase since the start of ship-to-ship bunkering activities near the island in 2016.
- NMU MSc student Praxedes Rukuni, supervised by Lorien Pichegru, Giannina Passuni and Shaun Deyzel from SAEON, is investigating food web stability in Algoa Bay using meso-zooplankton functional diversity metrics. Her research was delayed due to the closure of laboratory facilities at NMU during the COVID-19 lockdown, but she managed to complete all her data analyses by the end of the year. She found differences in the diets of anchovies eaten by African Penguins from St Croix and Bird Island in Algoa Bay. Anchovies targeted by the Bird Island penguins fed mostly on large crustaceans, whereas anchovies targeted by St Croix penguins fed on a wider range of smaller, less energetically beneficial prey, reflecting the less productive waters close to St Croix.
- Another NMU MSc student, Catherine Currin, was also severely delayed by the pandemic, but managed to measure the levels of stress hormones in blood samples from various captive penguin colonies. She will explore the use of an electronic heart rate recorder to compare physiological stress levels caused by several stressors, such as human, conspecific or predator encounters.
- Former NMU post-doc, Giannina Passuni, mentored by Lorien Pichegru, submitted her paper on the contribution of penguin guano from St Croix Island on water quality and productivity around the colony. She estimated that 45.4 tons of nitrogen (N) and 8.4 tons of phosphorus (P) were produced annually by the birds although only 5-20% of the N washed into the ocean. As part of her work and collaboration with Paula Patrick from SAEON, another paper on the island mass effect on the retention rate of larval fish was submitted to Estuarine and Coastal Shelf Science.
- NMU PhD student Katharina Reusch continued her study of the foraging ecology of Kelp Gulls Larus dominicanus. Her paper tracking Kelp Gulls from various South African colonies in Movement Ecology showed that breeding gulls relied less on anthropogenic habitats than predicted, even when colonies were close to large landfill sites, where many gulls scavenge. Stable isotope analyses of Kelp Gull adults and chicks confirmed their heterogeneous diet, and their focus on natural foods when raising chicks. In collaboration with former SANCCOB vet, Nola Parsons, she also has compared blood and intestinal parasite loads among colonies.
- David Grémillet and Lorien Pichegru continued their long-term study tracking the foraging ranges of Cape Gannets breeding on Malgas Island, which was initiated in 2002. As part of this collaboration, a paper was published in Animal Behaviour suggesting that the elaborate dance ceremony adult Cape Gannets perform each time they return to the nest may contain information about individual foraging behaviour. Dance duration is inversely related to the distance to the main foraging grounds. Pierre Pistorius also continued annual tracking of Cape Gannets from Bird Island.
- Zanri Strydom started a PhD at NMU on the foraging behaviour of Cape Gannets in relation to their age and experience, co-supervised by Herve Fritz and Jan Venter from the George campus of NMU, and David Grémillet and Lorien Pichegru. Zanri went to Malgas Island with Lorien in November and together they sampled 37 individuals of known-age.
- Nosipho Gumede started an MSc at UCT, supervised by Newi Makhado, Mduduzi Seakamela and Peter Ryan, on long-term variation in the diet of Cape Fur Seals Arctocephauls pusillus, and the potential for competition with fisheries and seabirds.
- A study led by Richard Sherley using a Bayesian approach highlighted the rapid decline of African Penguins since 1989, confirming their Endangered status on the IUCN Red List. The results highlight the penguin colonies in urgent need of conservation actions.
- Lorien Pichegru co-authored a paper on the impact of fishing on Magellanic Penguins Spheniscus magellanicus as part of a long-term collaboration with the CENPAT from CONICET, Puerto Madryn, Argentina.
- Similarly, as part of a collaboration with Deakin University in Victoria, Australia, PhD student Grace Sutton published an article in PeerJ showing how African Penguins benefit from multi-predator assemblages with other seabirds, but are out-competed by predatory fish.
- Alistair McInnes published a paper in Ibis showing how calling behaviour of African Penguins at sea is dependent on social context and the prey species that they are targeting. This arose from research he conducted as a post-doc at NMU.
- Pierre Pistorius and Alistair McInnes, now at Birdlife South Africa, successfully tracked Cape Cormorants breeding at Dyer Island with GPS loggers for the second year.
- Ralph Vanstreels published some of the work he conducted during his post-doc at NMU. In one paper he demonstrated that African Penguins ingest both seashells and debris while foraging at sea. Seashells presumably serve as a calcium source for egg production. Results from a study that he led on external and blood parasites were published in Parasitology.
- Lorien Pichegru was promoted to Adjunct Professor at the Coastal and Marine Research Institute at NMU.
- Following the decision in 2019 to reduce Kelp Gull numbers at key seabird colonies to reduce predation, the predation rate by gulls on Cape Gannet eggs and chicks at Malgas Island decreased by an order of magnitude in 2020.
- Lorien Pichegru took part in a UN-organised workshop on Benguela Current Forage Fish management.
- Ten papers were published in peer-reviewed journals during 2020, including one on the impacts of a warming climate on Bank Cormorant Phalacrocorax neglectus breeding in Conservation Physiology.
BirdLife International; BirdLife South Africa; DSI-NRF CoE grant.
Research team 2020
Prof. Pierre Pistorius (NMU)
Prof. Res Altwegg (SEEC, UCT)
Prof. Peter Ryan (FIAO, UCT)
A/Prof. Lorien Pichegru (NMU)
Dr Maëlle Connan (NMU)
Dr Timotheé Cook (U. Paris)
Dr Rob Crawford (Oceans & Coasts, DEA)
Dr Jon Green (U. Liverpool)
Dr David Grémillet (FIAO, UCT and CNRS)
Dr Azwianewi Makhado (Oceans & Coasts, DEA)
Dr Alistair McInnes (NMU Post-doc and BLSA)
Dr Florian Orgeret (NMU Post-doc)
Dr Giannina Passuni (NMU Post-doc)
Dr Richard Sherley (U. Bristol)
Dr Andrea Theibault (NMU Post-doc)
Dr Ralph Vanstreels (NMU Post-doc)
Students: Katharina Reusch (PhD, NMU), Zanri Strydom (PhD, NMU), Catherine Currin (MSc, NMU), Nosipho Gumede (MSc, UCT), Praxedes Rukuni (MSc, NMU), Victoria Stockdale (MSc, NMU).