Relationship between intraspecific diversity and ecosystem services: role of fish stocking practices - iSERV

Intraspecific diversity is a major facet of biodiversity that is currently affected by human activities. Fish species are facing multiple pressures, such as climate changes, fishing and pollution. Fishes are supporting many ecosystem services for culture, hobbies and are subject to several management practices. Changes in their intraspecific diversity could therefore have impacts on aquatic ecosystems and associated services.

Objectives

In large peri-alpine lakes, Arctic charr (Salvelinus alpinus) is an important species for recreational and commercial fishing, and for ecosystem functioning due to its trophic position (top predator). Therefore, Arctic charr displays important social and ecological values in these great lakes. Nevertheless, charrs numbers are declining and for several decades, supportive breeding programs have been used to support charr populations. For instance, Lake Annecy, supportive breeding management practices have evolved through time, and until recently fish from Lake Annecy and Lake Geneva were restocked. Although they have a common origin, charrs from these 2 lakes have undergone very different environmental constraints in the last century, for example Lake Geneva has undergone important eutrophication, which can cause individuals to diverge due to different trophic conditions. Genetic and phenotypic divergences are therefore expected and hybridizations between individuals of different origins can strongly modify the genetic and phenotypic structure of the population in Lake Annecy, modifying the services supported by this population. The main objective of this project will be to understand the role of captive breeding in Lake Annecy on intraspecific diversity (genetic and functional) and ecosystem services (biomass production and regulation of the nutrient cycle).

Resources

iServ is a three-parts project aiming to :

1. link intraspecific diversity resulting from restocking to the nutrient cycle (regulating service) at individual and ecosystem scales with a mesocosm approach;
2. quantify in situ the effects of restocking on genetic diversity and fish biomass production (production service);
3. quantify local population (e.g., anglers) preference for Arctic charr conservation strategies.

To quantify functional differences between individuals of different origins (Annecy and Léman), we will measure several functional traits at the individual level such as metabolic rate, nutrient excretion rate, prey consumption and morphology. These different traits can indeed affect interactions in communities and can therefore be important factors to understand the links between intraspecific diversity and ecosystem services.

Then, the effects of functional differences on regulation and production services will be tested using a mesocosm approach. They will be inoculated with phytoplankton and benthic and pelagic invertebrates a few months before the introduction of fish from different origins (Annecy, Léman). For several months, surveys will be carried out to understand the effects on ecosystem services:

1. concentration of nitrogen, phosphorus and carbon (nutrient cycle);
2. gas exchange (CO2) with the atmosphere (carbon sequestration);
3. invertebrate communities (food webs support)

From 2018 to 2020, larvae from Lake Geneva and Annecy have been marked (on the otoliths) before being restocked in the Lake Annecy. Through collaboration with anglers, the otoliths and scales were recovered from fish caught between 2021 and 2023. This will allow to investigate the effects of restocking on the genetic structure and biomass production of charr in Lake Annecy.

Finally, a socio-economic survey will be conducted to understand the preferences of the local population (e.g., anglers) for different conservation strategies influencing water quality, Arctic chare populations and genetic varieties, and to estimate the impacts on the contribution to economic well-being of recreational fishing.

Participants

INRAE units involved

• CARRTEL Joint Research Unit - Alpine Center for research on trophic networks and limnic ecosystems
• DECOD Joint Research Unit - Dynamics and sustainability of ecosystems: from the source to the ocean
• RECOVER Joint Research Unit - Risks, ECO-systems, Vulnerability, Environment, Resilience
• BETA Joint Researche Unite - Theoretical and applied economics office

External partnerships

• SETE Joint Research Unit CNRS - Theoretical and Experimental Ecology Station
• Fishing fédération Haute-Savoie
• Approved Association for Fishing and the Protection of Aquatic Environments - Annecy