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

This project investigated the effects of Arctic char (Salvelinus umbla) restocking practices in alpine lakes on the links between intraspecific diversity and ecosystem services. Restocking can alter intraspecific diversity, indirectly affecting fish biomass and nutrient cycling, which are important services for fisheries and water quality. Nevertheless, the links between fish management practices and ecosystem services remain largely unexplored.

Approaches

The iSERV project consisted of three components in order to:

•  Link intraspecific diversity resulting from restocking to the nutrient cycle (regulatory service) at the individual and ecosystem scales using a mesocosm approach; 
• Quantify in situ the effects of restocking on genetic diversity and fish biomass production (production service); 
• Quantify the local population's preference for char conservation strategies.

Results

Studies conducted in Lake Annecy show that the current Arctic char population is highly dependent on stocking, as naturally reproduced individuals are very scarce. Fish from local fish farms and naturally occurring individuals had very similar genetic structures, growth rates and phenotypic traits, suggesting a close relationship between these origins. In contrast, fish from Lake Geneva fish farms were slightly genetically differentiated and showed higher growth rates. Despite contrasting stocking intensities, individuals from both fish farms contributed comparably to the population, indicating that the origin of stocked fish may influence their survival and contribution to total biomass, a key service for fisheries.

Laboratory experiments have revealed functional differences depending on the origin and date of spawning of the fish, particularly in terms of zooplankton consumption and ammonium excretion, with contrasting thermal responses. These variations suggest that restocking could alter the nutrient cycle and trophic functioning of the lake, particularly in a context of global warming.

Finally, a mesocosm experiment showed that Arctic char influence the structure of aquatic communities through top-down effects on zooplankton and that differences between origins could alter the abundance of certain taxa present in the community. The overall effects on ecosystem functioning were moderate. Overall, the project highlights that restocking practices affect intraspecific diversity and, possibly, associated ecosystem services.

Participants

INRAE units involved

• UMR CARRTEL - Centre Alpin de Recherche sur les Réseaux Trophiques et les Ecosystèmes Limniques - University of Savoie Mont Blanc
• UMR DECOD - Dynamique et durabilité des écosystèmes : de la source à l’océan
• UMR RECOVER - Risques, écosystèmes, vulnérabilité, environnement, résilience - Aix Marseille University
• BETA - Bureau d'économie théorique et appliquée

Partners

• SETE - Theoretical and Experimental Ecology Station - CNRS
• Fédération de pêche de Haute-Savoie
• AAPPMA - Approved Association for Fishing and the Protection of Aquatic Environments - Annecy Lac Pêche