The expansion of the world's fisheries and the decline in fish stocks have increased conflicts between humans and marine megafauna. These conflicts result from negative interactions that are either direct (bycatch and/or depredation on catches) or indirect (competition for resources). They have socio-economic costs for the human communities dependent on the fishing activity and they impact the survival of the megafauna species and the ecosystems involved. However, long-lasting solutions for coexistence between fisheries and marine megafauna, which require inter- and trans-disciplinary research to be identified, remain limited. Therefore, the aim of my PhD is to produce integrated knowledge that can help in identifying the conditions required for megafauna species conservation, the sustainability of exploited resources and the socio-economic viability of the fishing activity. Specifically, under a co-supervision combining social sciences and marine ecology, I will use the principles of Sustainability Science and a multi-site approach (longline fisheries - marine megafauna conflicts in the French Southern lands and in New Caledonia) i) to understand both the anthropogenic and ecological drivers and consequences of these conflicts, and ii) to examine new management approaches that can ensure the sustainability of the whole socio-ecosystems involved.

Managing conflicts between humans and marine predators is hampered by limited knowledge on the ecological and behavioural mechanisms leading species to interact with humans. Among these mechanisms, the drivers of variation in the propensity of individuals to take risks by approaching humans, including the role of personality traits, remain poorly understood. The killer whale is among the species most frequently involved in conflicts with humans in the marine environment, mainly through depredation on fishery catches, a behaviour that has been acquired by many populations of the world. From the case conflict associated with killer whales feeding on fisheries catches around the Crozet islands, the main objective of my PhD project is to examine how inter-individual heterogeneity in behaviours are associated with variation in personality traits, and to investigate how these traits contribute, among other factors, to the response of individuals to a human activity involving risks and how they influence population dynamics.

Killer whales play a fundamental role in many marine ecosystems as apex predators affecting food web dynamics. However, within the Southern African Subregion (split between southern Africa and the Southwest Indian Ocean [SWIO]) many knowledge gaps and a lack of regional understanding regarding connectivity, predatory behaviour, demographics and ecosystem impacts persist. These data remain vital to understanding the species in general, its ecosystem use, impacts on other species within the ecosystem, and for conservation management. Additionally, depredation has and is affecting longline fisheries targeting tuna and Patagonian toothfish throughout the region, resulting in major economic losses, conservation concerns, and unquantified ecosystem effects, all of which are devoid of assessment for southern Africa specifically. My PhD project aims to establish a baseline of ecological understanding for the species both locally around southern Africa and regionally throughout the SWIO, incorporating depredation as a likely contributor to role alteration. To achieve this a multifaceted approach using (i) genetics, (ii) stable isotopes, (iii) photo-identification and (iv) ecosystem modelling will be used to: (i) provide an evolutionary template for connectivity, identify populations, and assess gene flow, effective population sizes, and diversity; (2) act as a proxy for predatory behaviour and trophic interactions (skin), provide a timeline of potential dietary shifts (teeth); (iii) assess population size, health, movements and association with depredation; and (iv) quantify and understand the ecological role and ecosystem effects of killer whales with and without competing fisheries.

The socio-economic and ecological implications of depredation are especially strong in the Patagonian toothfish longline fisheries and the sub-Antarctic ecosystems they operate in. These fisheries have become the primary economic activity of sub Antarctic waters and vessels experience high levels of depredation by two large toothed whale species; killer whales and sperm whales.  The amount of fish these species remove from the fishing gear pose a real challenge for the assessment of targeted stocks, and the behaviour is known to impact depredating killer and sperm whale populations, which are subject to high conservation concerns. Together with the socio-economic costs depredation incurs to fishers and fishing companies, these impacts make the development of mitigation solutions a priority.  However, these solutions are still hampered by a lack of understanding of the natural feeding ecology and distribution of the whales, and the factors determining their decisions to switch behaviour to depredation. Therefore, using satelite tracking data collected for 35 killer whales in the southern Indian and Altantic oceans, my research project addresses three key research questions: 1)  what areas killer whales use as foraging grounds in absence of fishing vessels? 2) to what extent do these areas overlap with those use by fisheries? 3) At what distance and during which stages of fishing operations do toothed whales detect fishing vessels? 

Killer whales of the Crozet islands have undergone a sharp decline in the late 1990s / early 2000s. This additive mortality event was largely due to whales being exposed to lethal control practices when interacting with illegal fisheries and was shown to have deeply affected the social organisation of the population. However, to what extent kinship drives this social organization is still poorly known.

Therefore, using both photo-identification data and tissue samples, the aim of my study is to characterize the social organisation of the Crozet’s killer whales over the last two decades, their genetic diversity and the pedigree (kinship) among them.

I have been working on conspecific aggression in killer whales as part of my MSc at the University of Montpellier. The project involves using conspecific scars visible in photo-identification images as a proxy for physical interactions and aims to determine whether prey preferences and social structure influence scarring rates by comparing three distinct populations: the "Bigg's" and "Northern resident" killer whales in British Columbia, and the killer whales of the Crozet archipelago. It also considers whether demographic factors such as age and sex may influence physical interactions as well as how conspecific scars heal over time. The work is a collaboration between the UMR MARBEC (France) and Bay Cetology (Canada).