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Paul Tixier, Nicolas Gasco, Jared R. Towers, Christophe Guinet. (2021). Killer whales of the Crozet Archipelago and adjacent waters: photo-identification catalogue, population status and distribution in 2020.
Abstract: Three forms of killer whales (Orcinus orca) occur around the subantarctic islands of the southern Indian Ocean (42-53°S; 34-74°E). The form encountered in both inshore and offshore waters, described as generalist in its feeding preferences (seals, whales, penguins and fish as prey) and known to depredate toothfish from longliners has been opportunistically photo-identified around the Crozet archipelago since the 1960s. Together with photo-identification data collected in the Prince Edward/Marion EEZ, Kerguelen EEZ and international waters, this report provides up to date information on the abundance and distribution of the Crozet killer whales. In total, 124,313 photographs taken during 2,109 encounters since 1964 were analysed, allowing for 299 individuals to be identified. Most encounters with available data were from the Crozet EEZ (1,432 from longliners, 602 from Île de la Possession) and occurred after 2003 when photo-identification was implemented in the fishery observer program. Among the 188 individuals recorded in the Crozet EEZ since 2003, 22 (12%) were also photographed in the Kerguelen EEZ, 13 (7%) in the Prince Edward/Marion EEZ and 13 (7%) in adjacent international waters. The frequently encountered subset of the Crozet killer whale population was composed of 23 social units (maternal groups), 19 of which included individuals alive in 2020. These social units ranged in size from 1 to 11 individuals with a mean (± SD) of 4 ± 3 per unit. As of June 2020 when the latest photographs included in the study were taken, abundance of this subset was 89-94 individuals. However, detailed analysis of data collected between 2005 and 2020 shows that the number of confirmed deaths (n = 51) exceeds the number of recorded births (n = 46), resulting in a 5% decrease of the population size over this period. These deaths were distributed across the population with the majority occurring in the most common sex and age classes – adult females and juveniles. Factors contributing to mortalities are unclear, but may include lethal interactions with illegal fisheries. When paired with the fact that the Crozet killer whales already underwent a severe mortality episode in the 1990s, these findings raise strong concerns about the future of the population and stress the necessity of conservation actions while maintaining an intensive monitoring effort.
Programme: 109
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Téchiné P., Testut L. (2018). Présentation du SNO SONEL-ROSAME.
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Hullé M., Buchard C., Renault D., Lebouvier M., Vernon P. (2017). Distribution patterns of invertebrate species introduced into the sub-Antarctic Kerguelen Islands.
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Gadea A., Le Lamer A.-c., Fanuel M., Boustie J., Charrier M., Le Dévéhat F. (2017). Overcoming specialized metabolites by gaining essential nutrients: a lichen/snail case study.
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Fourcy D., Chapuis J.-l., Lebouvier M., Robin M. (2016). Dynamique de la végétation des îles Kerguelen et changements climatiques.
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Zitterbart D.P., Le Bohec C., Nesterova A., Richter S., Schneider W., Fabry B. (2014). Long-term monitoring of penguin behaviour, population dynamics and colony structure.
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Whittington J.D., Le Maho Y., Boureau M., Morinay J., Amelineau F., Le Bohec C. (2014). Acoustic features of display calls may reveal breeding status and individual quality in emperor penguins.
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Swadling, K., Koubbi, P., and ICO²TAKs scientists. (2016). Influence of fast ice on zooplankton and fish in Dumont d'Urville (East Antarctica).
Abstract: NIPR Symposium
Zooplankton that live at high latitudes are influenced by seasonal cycles in primary productivity, the strength and position of major oceanographic
currents and the growth and decay of sea ice. Zooplankton are important prey for fish, especially in sheltered coastal regions that act as nurseries for larvae and juveniles.
To describe the influence of sea ice dynamics on the long term distribution of zooplankton and, in turn, their availability as prey for fish, sampling in the fast ice zone near Dumont d’Urville Station, located along the coast of Adélie Land in east Antarctica, has been carried out continually from 2000.
In the last fifteen years there have been five annual and ten summer field surveys that have sampled the underice zooplankton and ice-associated
fish, focussing on the stomach contents of the fish and abundance and diversity of the zooplankton. The fast ice of the region has been mapped via
satellites since 2001. Sampling of the sea ice itself began in 2003, with the ice meiofauna counted and identified from multiple ice cores.
The species of zooplankton recorded for the coastal region are typical of other Antarctic coastal areas and consist of small copepods such as Oithona
spp., Oncaea spp. and Stephos longipes, larger copepods including Metridia spp. and Calanoides acutus, meroplanktonic larvae, appendicularians and euphausiids. Meiofauna in the fast ice is dominated by copepods, particularly Drescheriella glacialis, Paralabidocera antarctica and Stephos longipes.
The abundance of zooplankton has varied at least 10-fold between years, producing consequences for the fish species that prey on them: in years of low zooplankton abundance the gut fullness of the fish is correspondingly low.
Programme: 1142
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Lamarque, G., Bascou, J., Ménot, R.P., Paquette, J.L., Rolland, Y., Cottin, J.Y. (2015). George V Land paragneisses xenoliths dating. New insights for the Antarctica-Australia connection and geodynamic reconstructions.
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Julien Jumelet, Slimane Bekki, and Philippe Keckhut. (2017). Microphysical modelling of volcanic plumes / Comparisons against ground based and spaceborne lidar data (Vol. 19).
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