The French National Research Institute for Agriculture, Food, and the Environment (INRAE) is a public research establishment. It is a community of 12,000 people with more than 200 research units and 42 experimental units located throughout France. The institute is among the world leaders in agricultural and food sciences, in plant and animal sciences, and is 11th in the world in ecology and environment. INRAE’s main goal is to be a key player in the transitions necessary to address major global challenges. In the face of the increase in population, climate change, scarcity of resources and decline in biodiversity, the institute develops solutions for multiperformance agriculture, high quality food and sustainable management of resources and ecosystems.


You will be welcomed in the unit EABX Aquatic ecosystems and global change, INRAE Nouvelle Aquitaine, in the FREEMA team (Functioning and Restoration of Estuarine Ecosystems and Amphihaline Migratory Populations).

 Context:

The Gironde-Garonne-Dordogne (GGD) watershed system hosts the last wild population of European sturgeon, the largest diadromous migratory fish in Western Europe classified as critically endangered. Conservation and restoration programs are ongoing in Germany and France since the 1990s, with the last reproduction in the wild observed in 1994 in the Gironde area. The species is subjected to a re-introduction program with more than 1.7 million of juveniles released in the Garonne and Dordogne rivers between 2007 and 2015. This anadromous migratory species, born in the lower sections of rivers, migrates during its first year of life towards the estuary to grow and then reach the sea to continue its growth before returning to rivers to spawn at around 12 and 16 years of age for males and females, respectively.
The estuarine environment, more particularly the Gironde estuary, and the sea represent the major growth area of the European sturgeon. Habitat use by wild individuals was studied in the Gironde estuary during the 1990s for individuals of 4 to 5 years of age. Downstream migration patterns of reintroduced individuals, as well as their habitat uses within the estuarine oligohaline section, were also analyzed. However, we know little on exchanges between estuarine and marine systems, as well as the species growth stage at sea. This is due to difficulties to collect direct information on the species movement patterns between the estuarine and marine systems. In order to better understand the fate of individuals reintroduced into the GDD system since 2007, and therefore to improve the condition of success of these restoration actions, it appears essential to understand the species’ migratory patterns at the estuary-sea interface. Given the critically endangered status of the species, such analyses must rely on non-lethal techniques.
This work represents a methodological and ethical challenge related to the conservation status of the targeted species, in particular with regards to search for relationship between organs classically used and the application of non-lethal techniques with low invasive sampling (fins). The challenge principally holds into the reconstruction of migratory patterns characterizing the reintroduced population. The convergence of multiple chemical tracers, with their respective advantages and limits, which will be deeply discussed within a consortium built from three research laboratories from the Nouvelle-Aquitaine region (UMR 5808 EPOC Bordeaux, UMR 7266 LIENSs La Rochelle, UMR 5254 IPREM Pau) appear to us as the ideal approach to tackle this challenge.
Finally, some questions are being raised within the scientific and socio-economic networks interested into European sturgeon restocking program: what are the adaptive capacities of individuals raised in captivity once released in the wild? What cost/benefit ratio of re-stocking?. European sturgeons are being released in the wild at various ages (1 year). Habitat use patterns and migratory tactics will therefore also be analyzed as a function of this possible effect of captivity history, with the objective of improving the restoration practices.
This postdoctoral project is part of a larger project named ‘REVE’ (REconstruction des tactiques de Vie de l’Esturgeon européen) funded by the Nouvelle-Aquitaine Region and the Water agency Adour-Garonne. The general objectives of the REVE project are embedded within the national strategy for knowledge improvement on the ecology of the species within the National Action Plan (NAP) in favor of the species restoration.

 Specific objectives and tasks:
Based on the context detailed above, specific objectives of the proposed work are to:
1) Compare measurements of various chemical tracers (isotopes, contaminants) between different organs, and estimate the statistical relationships between them, with the perspective of developing non-lethal sampling methods for the application of chemical tracers.
2) Reconstruct migratory patterns of European sturgeon between the Gironde estuary and the adjacent marine coastal environment from isotopic (δ13C, δ15N, δ34S, δ87Sr) or other (Sr :Ca, Ba :Ca) chemical tracers measured in the fin and/or pectoral fin rays, in order to identify the importance of the connectivity between the estuary and the sea for the species, and the existence of one or several migratory tactics within the population. This objective will be completed through collaborations with expert partners of the project (UMR 5805 EPOC, Bordeaux : UMR 7266 LIENSs, La Rochelle), who will provide data on the isotopic and chemical composition of resources and/or water masses from the targeted estuarine and marine habitats.
3) Identify the potential effects of time in captivity on the migratory tactics developed by the organisms.
4) Improve knowledge on the European sturgeon life stage at sea, in particular through the estimation of contamination risks.

The postdoc will first realize a review of the scientific literature in order to select the most appropriate chemical tracers allowing for the estimation of estuary-sea migrations in large mobile fishes. He/she will consult the academic experts associated with the project in order to validate the analytical procedures to be applied for the selected tracers. She/he will then conduct the laboratory work required for the different sets of analyses, and collaborate with partners from the project in order to link obtained information at the scale of individual sturgeon fishes, with information on sources data from the targeted estuarine and marine habitats

The postdoc laboratory work will benefit from approximately 100 fin samples of Acipenser sturio collected during the « Sturat » sampling program in the Gironde estuary. The analysis of multiple isotopic tracers within this biological material will allow the estimation of recent exchanges at the estuary-sea interface for sturgeons of different ages/sizes and which have spent various times in captivity before being reintroduced into the estuary. In this regards, a selection of fin samples to be analyzed will be performed as a function of fish size, age and captivity history. For the same individuals with fin samples available, fin rays are available and analyses of δ87Sr, Sr :Ca and/or Ba :Ca ratios can be conducted using femtoseconde laser ablation coupled with quadripolar (Sr :Ca, Ba :Ca) and multicollection (87Sr :86Sr) mass spectrometers in order to reconstruct migratory trajectories of individuals on a longer time scale (collaboration with UMR5254 IPREM CNRS/UPPA).

In addition to the aforementioned preserved fin samples, the postdoc laboratory work will also rely on 6 sturgeon fish that were incidentally caught at sea and preserved frozen at our laboratory at -20°C. Those individuals will help to calibrate tracers’ measurement between the different organs and their life histories at sea since they left the Gironde estuary will be analyzed. They will complete preliminary comparisons of isotopic measurements between organs initiated from 5 sturgeon fishes euthanized in captivity. Organic and inorganic contaminants in the different organs will also be analyzed (collaboration with UMR EPOC). This will help in assessing possibilities of non-lethal sampling on sturgeon fishes, and to inform on the contamination risks encountered by the reintroduced fish while at sea.


Interested candidates must hold a PhD in aquatic ecology, biological oceanography or biochemistry applied to aquatic ecology.

An experience of the theoretical principles and practical applications of some or all of the contemplated chemical tracers for studying mobile animal movements or habitat use in aquatic environments is required. The publication of previous results based on this type of methodology, and highlighting the associated theoretical and practical knowledge, is therefore desirable. Experience with applying laboratory techniques for sample preparation is also needed (as the candidate will conduct laboratory work him/her-self).

A good knowledge and experience of statistical approaches needed for the interpretation of multiple tracer data is also expected (univariate and multivariate statistical techniques, mixed models etc.). Capacities to propose innovative avenues of research and to elaborate a realistic work plan in autonomy, together with good relational abilities, will also be appreciated.

Candidates must be able to speak and write in English. For non-French speaking candidates, the ability to communicate in French in a professional context would be appreciated.

By joining our teams, you benefit from (depending on the type of contract):
– until 30 days of annual leave + 15 days « Reduction of Working Time » (for a full time);
– parenting support: CESU childcare, leisure services;
– skills development systems: training, career advise;
– social support: advice and listening, social assistance and loans;
– holiday and leisure services: holiday vouchers, accommodation at preferential rates;
– sports and cultural activities;
– collective catering.

 Reception modalities

 Unit: EABX Aquatic ecosystems and global change
 Postal code + city: 33612 Gazinet Cestas
 Type of contract: CDD temporary position
 Duration of the contract: 2 years
 Starting date: 1st of December 2021
 Remuneration: indicative gross monthly salary between 2516 and 2736 Euros
 How to apply

The submission must include 1) a detailed CV, 2) a motivation letter (2 pages maximum) in which candidates will explain their competencies with regards to the specific objectives and methodologies of the project, 3) one to two publications related to one or several of the methodological approaches contemplated for the project, and 4) a one-page document in which the candidate will explain how she or he wishes to tackle the objectives and challenges of the postdoc. The submission file must be sent as a single pdf to Marie-Laure Acolas ( and Laure Carassou ( by the due date.

 Deadline for applications: September 12, 2021
Application will be evaluated during the week of the 13rd of September and the candidates whose applications have been selected will be auditioned by videoconference during the week of the 20th of September 2021.

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