MODESTA
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Response of migratory fish populations to climate change: an approach using size-structured demographic models |
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Environmental disturbances linked to anthropogenic pressures, such as climate change, are affecting ecosystems functioning and the sustainability of natural resources. These disturbances are particularly marked in aquatic ecosystems along the land-sea continuum, which provide ecosystem services to the society. A better understanding of the mechanisms that control the response of fish populations to multiple stress factors is needed to anticipate the impact of changes on ecosystems and fisheries resources, and to better inform their management.
Body growth is an integrative trait shaped by evolutionary trade-offs, integrating the ability of individuals to acquire food resources from their environment, assimilate and allocate them to different functions (migration, reproduction, survival). Thus, any change in growth in response to environmental variations (e.g., temperature, food resources) will have profound repercussions on the demographic structure and the population dynamics and resilience.
However, growth-dependent mechanisms are poorly understood, and population dynamics models (particularly fish stock assessment models used to evaluate the status of fish populations) rarely incorporate these sources of inter-individual heterogeneity and temporal variations. Improving our understanding of growth-dependent demographic mechanisms is paramount to better understand the response of populations to environmental changes, anticipate their capacity to adapt to future changes and propose appropriate management measures.
The MODESTA project aims at improving our understanding of the growth-dependent mechanisms that control the response of Atlantic salmon (Salmo salar) populations to climate change, in order to anticipate the impact of changes on these populations and inform management. This migratory fish is an emblematic fishery and heritage resource. It is a sentinel species for assessing the effects of global change on ecosystems and biodiversity in the land-sea continuum. For several decades now, there has been a worrying decline in the abundance of wild salmon populations around the world, largely attributed to a drop in survival at sea. In parallel with this decline in survival, a decrease in age at maturity and adult size has been observed. These rapid changes suggest a response to ecosystem modifications linked to a decline in the quantity and quality of food resources available to salmon in the Atlantic Ocean.
The aim is to better describe how variations in growth are propagated along the salmon life cycle, and what are the impacts are on the population structure (age classes, sex ratio, size distribution) and dynamics. The expected results are a better representation of the demographic mechanisms, and an improvement in the predictive capacity of population dynamics models to inform the implementation of management measures in the context of climate change. The methodological approach is to develop population models structured by age, sex, life stage and size. These models are based on long-term monitoring of wild populations (estimation of abundance and population structure at different life stages, reconstruction of individual growth trajectories based on scale analysis). A major methodological challenge is to develop models representing demographic processes not directly accessible to observation (e.g., demographic transitions during marine life). To this end, an innovative modelling approach will be developed, based on the coupling of two conceptual framework: i) population models structured according to age, stage and size (“Integral Projection Models”); and ii) hierarchical statistical models (“Integrated Population Models”), enabling all available data to be exploited within a unified framework. The consequences of variations in growth will be explored by analysing historical series and projections to test short- and medium-term scenarios of environmental change. This approach will be fed by existing data from long-term monitoring of wild populations of Atlantic salmon in Brittany and Europe. In particular, the project will capitalize on data from the Observatoire de Recherche en Environnement Petits Fleuves Côtiers and the Centre National pour l'Interprétation des Captures de Salmonidés, centralized in information systems managed by INRAE in Rennes.
People involved
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BOULAIRE Eliot, Doctorant Email : eliot.boulaire@institut-agro.fr |
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NEVOUX Marie, Scientist Phone : +33 2 23 48 50 15 Email : marie.nevoux@inrae.fr |
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RIVOT Etienne, Scientist Phone : +33 2 23 48 59 34 Email : etienne.rivot@institut-agro.fr |