Description du sujet de thèse

The thesis is funded by the CNRS Mission for Transverse and Interdisciplinary Initiatives, 2025 laureate. Marine ecosystems, essential to human well-being, are threatened by climate change. To ensure effective conservation measures in the face of these upheavals, a holistic approach is necessary. This must integrate the plurality of knowledge, in particular local ecological knowledge (LES) and the values of local communities, with scientific knowledge, notably through the development of innovative tools. The main mission aims to integrate local ecological knowledge (LES) and environmental DNA (eDNA) metabarcoding in order to assess the distribution of marine biodiversity and the plurality of values associated with it in the Western Indian Ocean, particularly in Kenya and Tanzania. The main objective of this thesis is to better integrate the plurality of values (ecological, economic and sociocultural) as well as the representations of local communities into reflections on a more sustainable management of fisheries resources in the face of climate change.

The first objective will be to identify the marine species and geographical areas that present the greatest values for communities (e.g., heritage value, attachment to the place). The second objective will be to determine the ecological value of these marine areas and the distribution of key teleost and elasmobranch fish species using environmental DNA and capture data. Finally, the third objective will be to assess the preferences of local communities for different protection scenarios produced by combining the local and scientific knowledge studied. By mobilizing an interdisciplinary approach, this project will establish a fundamental framework bringing together various knowledge systems to better guide management measures that reconcile conservation objectives with the expectations, values, and needs of local populations.

Contexte de travail

The recruited person will co-construct the objectives and methods of the thesis project with partners and stakeholders by adopting a mixed-methods approach. The recruited person will combine participatory mapping approaches, semi-structured interviews and focus groups to identify marine areas (spawning grounds, subsistence fisheries, coastal protection), species of interest to the communities and associated values (economic, socio-cultural and ecological). Specific questions will be asked about perceptions of environmental changes and their impacts (species displacement, abundance, biology, unusual events). The recruited person will be responsible for applying this approach at two sites, where he or she will spend three months each immersed in the daily activities of the communities (participant observation), to better understand their functioning and value system. Based on participatory maps, several areas will be selected for water sampling that will allow inference of the presence and relative abundance of teleost and elasmobranch fish via eDNA metabarcoding.

Two sets of primers will be used for each group. The metabarcoding results will allow the recruited person to assess biodiversity in the selected areas (inside and outside MPAs) and to map their ecological values based on complementary diversity indices (taxonomic, phylogenetic and functional), trophic structure, and the proportion of vulnerable species. These data will be supplemented and validated with complementary scientific sources, including catch-at-landing data, provided by the project partners (KMFRI in Kenya and the Ministry of Fisheries in Tanzania). Finally, Joint Species Distribution Models (JSDM) will be used to predict community changes and species presence by the end of the century. Based on data on local and scientific knowledge, the recruited person will have to define four key attributes inspired by the concept of Other Effective Conservation Measures (e.g., food, cultural and ceremonial values, role as a buffer against climate change).

These attributes, linked to the values identified during the interviews, will reflect the priorities of communities and stakeholders. These attributes will be used to develop approximately 12 alternative conservation scenarios. The recruited person will then be responsible for analyzing community preferences for these scenarios via a discrete choice experiment (DCE). This approach will estimate marginal preferences for attributes, willingness to pay for a unit change in each attribute, and identify trade-offs between the different perceived benefits. The DCE will be conducted by the recruited person with stakeholders (fishermen, managers) through workshops and individual questionnaires in villages and landing sites. Each scenario will be presented visually to facilitate their understanding. This thesis is part of the international MESCAL project (Multiscale connectivity at species and community levels to achieve conservation goals under climate change in the Western Indian Ocean) funded by the French National Research Agency, the French Development Agency, and several African funding agencies.

MESCAL brings together a consortium of 14 scientific partners in Kenya, Tanzania, Mozambique, and South Africa. The recruited person will benefit from the support of local collaborators, particularly in Kenya (Kenya Marine and Fisheries Research Institute, Wildlife Research and Training Institute) and Tanzania (State University of Zanzibar, Institute of Marine Sciences). The MESCAL budget will cover all operating costs of the thesis, including field missions, metabarcoding and associated bioinformatics, workshops, surveys, and possibly funding for local students who will work with the recruited person.
The recruited person must have an academic background in ethnoecology or anthropology, complemented by experience in ecology, particularly in community ecology or conservation. Training in environmental genomics will also be considered, provided that the person demonstrates experience and a real interest in ethnoecological approaches and fieldwork with local communities and stakeholders. The recruited person must master mixed approaches to ethnoecological data collection in the field, such as semi-structured interviews and facilitating focus groups. Good command of biostatistics (database management, use of R software) as well as an excellent level of English are essential. As eDNA data are amplified and sequenced independently, the involvement of the recruited person in their in-depth analysis will depend on their interest and skills. However, the recruited person will participate in the collection of these samples. Finally, the person recruited will have to demonstrate autonomy, adaptability and initiative, particularly in the context of extended field missions in Kenya and/or Tanzania, in sometimes constrained logistical contexts.
As a member of the UMR MARBEC, the recruited person will have a personal amount of €1,500 for 3 years that he/she can use for his/her activity (conference fees, specific training, etc.). The supervision of this thesis will be provided by an interdisciplinary team within the MESCAL project. Thomas Lamy (MARBEC), co-PI of MESCAL, is an expert in modeling changes in marine biodiversity. He will bring unique expertise in combining molecular techniques (eDNA) and modeling for the conservation of marine biodiversity, and recent experience at the human-nature interface. Georgeta Stoïca (University of Mayotte), anthropologist, is a specialist in social representations of coral ecosystems and conflicts related to access to natural resources. Céline Reisser (MARBEC), marine population geneticist, will support the student on the genetic aspects of the project. Delphine Renard (CEFE), will bring her experience on the knowledge of local communities. The surveys will be developed in consultation with regional partners to ensure the project's success and student safety. Fieldwork will be conducted primarily in Kenya and Tanzania, hosted by MESCAL project partners.
The recruited person will participate in the eDNA sampling campaigns with Peter Teske (University of Johannesburg) and Romina Henriques (University of Pretoria), but DNA extraction and sequencing will be carried out by a private company (e.g. ARGALY). Bastien Mérigot (MARBEC) will bring his expertise in biodiversity modeling, while Christopher Bova (Rhodes University) will contribute to the development and analysis of the ECDs. Workshops between the different members of the project, particularly during the construction of the DCEs, may be organized. The recruited person will also work within the large research consortium MESCAL, and will be required to present and discuss these results, and contribute to sampling missions along the East African coast according to his or her interest. In addition, the recruited person will be invited to interact with other students of the GDR OMER, which funds the thesis scholarship, and to present his or her results each year at the OMER days.

Contraintes et risques

Finally, the recruited person will need to demonstrate autonomy, adaptability, and initiative, particularly in the context of extended field missions in Kenya and/or Tanzania, in sometimes logistically constrained environments.
All travel, particularly to identified high-risk areas, will be subject to CNRS regulations regarding duration and will require a prior request and approval from the CNRS.Defense Security Officer.
The recruited person will have access to an office and the necessary equipment to carry out their work. They will also have access to Ifremer's Datarmor computing cluster.