Unprecedented data on the presence of anadromous migratory fish at sea

A team of researchers from several institutions, including the French Biodiversity Agency (OFB), has developed a new modeling approach to gain a better understanding of the distribution of anadromous migratory fish at sea. This method, applied to threatened species such as shad and the European eel, has led to major advances in their management at sea.

Anadromous migratory fish are species that spend part of their life cycle at sea, and another part in freshwater. They are particularly threatened by the pressures exerted by human activity, such as agricultural runoff and contaminants, habitat destruction, obstacles to migration, fishing and climate change. Throughout their life cycle, they may encounter these difficulties as they move between freshwater and marine environments.

Unprecedented data to protect anadromous migratory fish

This study has made it possible to test a new approach to modeling the distribution of these fish, whose life phase at sea is poorly understood. Indeed, to date, no model detailing their spatial distribution at sea exists. As part of the “MigrenMer” project, the team of researchers gathered some 170,000 scientific and commercial fishing data over the last 60 years. Analysis of this data revealed the areas frequented at sea by eleven species of anadromous migrants.

55% of habitats located inside Marine Protected Areas (MPAs)

The researchers discovered that 55% of the main habitats occupied by anadromous migratory fish are located inside in marine protected areas, designed to protect these migratory species. Of these protected areas, only half have specific measures in place to protect the species. For instance, less than 30% of the main habitat of the endangered Mediterranean shad (Alosa agone) is located inside MPAs. But other species such as the European eel and the European smelt have around 70% of their main habitats within MPAs, of which only 9% have specific measures to protect the European eel, currently classified as “critically endangered” by the IUCN. Finally, no specific measures are in place to protect the European smelt.

This modeling approach could be useful for other marine species with rare occurrences (fish, rays, sharks, etc.), and in particular threatened species that could benefit from conservation measures within MPAs. The “MigrenMer” project was led by the “Cluster for the management of anadromous migrants in their environment” (MIAME), made up of experts in anadromous migratory fish from several French research institutes: OFB, National Research Institute for Agriculture, Food and the Environment (INRAE), the Agro Institut and the University of Pau and Pays de l'Adour (UPPA). This project complies with two European directives, the Habitat-Fauna-Flora Directive (DHFF) and the Marine Strategy Framework Directive (DCSMM), and has received funding from the MIAME Cluster and the Water and Biodiversity Directorate (DEB) of the French Ministry for Ecological Transition and Territorial Cohesion.