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. In 2019, the sardine fishing industry virtually collapsed, with no catches made on the west coast and <1000 tons caught in Algoa Bay. Conditions for African Penguins Spheniscus demersus, Cape Cormorants Phalacrocorax capensis and Cape Gannets Morus capensis breeding at west coast locations were at their poorest recorded since the beginning of the long-term study initiated at the Fitz in 2002 for gannets and 2007 for penguins. Worryingly, numbers of penguins breeding in Algoa Bay, which has supported more than half the world population in recent years, also fell sharply, mainly due to a population collapse on St Croix Island. 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 2019
- Alistair McInnes completed his post-doc at NMU on the use of seabirds as real-time monitors of pelagic fish availability. Working mainly at Stony Point, Betty’s Bay, home to the only increasing population of African Penguins, he used penguin cameras, GPS loggers and weigh-bridges to measure how hard penguins have to work to catch prey. In a paper published in Ibis, he demonstrated penguin calling behaviour depends on the number of penguins in the vicinity as well as on the prey that they target. Solitary birds call more often than birds in groups, highlighting the importance of gathering in groups to increase foraging efficiency when targeting schooling prey. In another paper he showed how prey herding by African Penguins benefits a number of other seabird species such as Sooty Shearwaters Ardenna grisea and Cape Cormorants. This process of facilitation demonstrates the import role penguins plays in the functioning of local marine ecosystems.
- Former NMU post-doc and vet, Ralph Vanstreels, continued to publish papers from his research while at NMU. He summarised post-mortem examinations of penguins found dead at mainland breeding colonies to describe the injuries characteristic of penguins attacked by leopards, caracals, domestic dogs and Cape grey mongooses.
- NMU MSc student Catherine Currin is exploring the use of a remote heart-rate recorder for African Penguins designed by an Honours student at NMU’s Department of Mechatronics, to contrast stress levels in wild and captive penguin colonies.
- NMU post-doc, Giannina Passuni, mentored by Lorien Pichegru and NMU’s Nadine Strydom, has been investigating the contribution of African Penguin guano from St Croix Island on water quality and productivity around the colony. She estimated that 45.4 tons of N and 8.4 tons of P were produced annually by the birds although only 5-20% of the N washed into the ocean. As a result, water quality and productivity were similar close to (200 m) and farther offshore (2 km) from the colony, suggesting limited influence of penguin excreta on the immediate marine environment.
- The experimental closure of commercial fishing for small pelagic fish around key penguin breeding islands continued in 2019, despite strong evidence that fishing close to breeding colonies has a strong adverse effect on African Penguins. Virtually the entire catch of sardine in 2019 was caught close to St Croix Island, the world’s largest African Penguin colony, where fishing was re-opened in 2018. Penguin breeding numbers at St Croix in 2019 halved from 2018 and were a third of 2015, resulting in calls being made to ban purse-seine fishing around African Penguin colonies. Sadly, no decision was made to institute permanent closures, and the waters around St Croix colony remain open to fishing. Penguins are under further pressure at this colony due to controversial ship-to-ship bunkering operations near the island, which has resulted in several spills that have oiled penguins and other seabirds.
- NMU MSc student Praxedes Rukuni, co-supervised by Lorien, Giannina and Dr Shaun Deyzel from SAEON, is investigating food web stability in Algoa Bay using meso-zooplankton functional diversity metrics. Praxedes compared the stomach contents of anchovies eaten by African Penguins to the diversity and biomass of zooplankton collected across the bay. Her aim is to calculate the functional diversity of the zooplankton community to infer the stability of the pelagic food web.
- Lorien also supervised NMU MSc student Tayla Ginsburg, who investigated how a Dynamic Ocean Management (DOM) plan could allow fishing to occur around colonies when fish abundance is high, thereby reducing the cost of local closures to the fishery. Although she found that such a plan could work, the current extremely low levels of fish stocks prevent such an approach.
- NMU PhD student Katharina Reusch continued her study of the foraging ecology of Kelp Gulls Larus dominicanus using a variety of approaches including tracking breeding adults, stable isotope analyses and conventional diet studies. She has found marked differences among colonies in terms of foraging areas and diet, but in general adult Kelp Gulls seem to rely less on strongly modified habitats, such as landfills, than expected. In collaboration with Dr Nola Parsons, she also has compared blood and intestinal parasite loads among colonies.
- Ilana Engelbrecht continued working on her MSc with Pierre Pistorius on foraging strategies and within-pair synchronization in Cape Gannets at Bird Island. The project is based on the extensive set of foraging trip durations of individuals tagged with VHF transponders.
- 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. With a team of students and volunteers, they monitored approximately 40 individuals of known-age to explore how experience influences foraging success. Gannet predation by Cape Fur Seals decreased thanks to active management by South African National Parks, however Kelp Gull predation on gannet eggs and chicks remained very high, leading to the start of active control measures against gulls in November 2019. Lorien was invited to a workshop organised by SANParks in April 2019 to advise on managing gull predation on seabird colonies.
- Pierre Pistorius continued monitoring Cape Gannets at Bird Island in Algoa Bay, and collected further tracking and demographic data from this colony. Post-doc Andrea Thiebault deployed acoustic recorders integrated with video-cameras on the gannets to better understand their vocal repertoire. Her paper in the Journal of Avian Biology showed how their calls at sea were context specific and probably improve foraging success.
- PhD student Emmanuel Adekola assisted with field work on Malgas Island while continuing his PhD on moult in Cape Gannets. He used the opportunity of working on known-age adults to test for age-specific differences in head coloration.
- A study led by Richard Sherley on the global threat status of Cape Gannets using a Bayesian approach concluded that the 45% decline in the last 50 years is slightly less than previously thought, and so the species may better fit the ‘Vulnerable’ rather than current ‘Endangered’ red list status. Nonetheless, the threats to the species are significant and include scarcity of natural prey, especially off the west-coast, predation by gulls and fur seals, and extreme weather events.
- MSc student Laurie Johnson was awarded her degree.
- Dr Alistair McInnes was appointed Seabird Conservation Programme Manager for BirdLife South Africa.
- Fourteen papers were published in peer-reviewed journals during 2019.
- Lorien Pichegru participated in a collaborative study exploring the use of reference points for predators in ecosystem-based management to fisheries, using the example of penguins and sardines in South Africa, which was published in Fish and Fisheries.
- Lorien and MSc student Tayla Ginsberg co-authored a paper in Frontiers in Marine Science on the key challenges to advancing an ecosystem-based approach to marine spatial planning in South Africa.
- Pierre Pistorius and two post-grads gave talks at the 10th International Penguin Conference in New Zealand. Pierre was invited to give a presentation advising early career scientists how to pursue a scientific career.
BirdLife International; BirdLife South Africa; DST-NRF CoE grant.
Research team 2019
Prof. Pierre Pistorius (NMU)
Prof. Res Altwegg (SEEC, UCT)
Prof. Peter Ryan (FIAO, UCT)
Dr 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)
Dr Ross Wanless (FIAO, UCT and BLSA)
Students: Emmanuel Adekola (PhD, UCT); Katharina Reusch (PhD, NMU); Gwendoline Traisnel (PhD, NMU); Catherine Currin (MSc, NMU); Ilana Engelbrecht (MSc, NMU); Tayla Ginsburg (MSc, NMU); Laurie Johnson (MSc, UCT); Praxedes Rukuni (MSc, NMU),