The professional glass eel fishermen on the Loire are patiently continuing their restocking efforts on the Loire, one of the major rivers on the Atlantic coast and at the centre of the European eel’s range.
After patiently defining the release zone, the glass eels, transported in part by an AFPMAR wholesaler, are released in the presence of a technician from the FishPass office, who ensures, among other things, that the glass eels are properly acclimatised to the temperature of the river before they are released.
The glass eels were marked, making it possible to obtain quantitative data on the survival of fry immersed in these areas.
Some might ask the obvious question: why capture glass eels in the lower estuary and release them further upstream? Why not simply let them migrate freely?
This is common sense, but unfortunately it comes up against the state of our aquatic environments.
Research carried out on the colonisation of catchment areas by glass eel flows shows that when they become pigmented, they migrate towards the bottom and acquire a quasi-territorial behaviour. This happens more quickly as the temperature rises. They then need a large surface area to grow and avoid excessive mortality in the lower reaches (linked to what are known as density-dependency phenomena).
However, over the last thirty years or more, the rivers have gradually been disconnected from their lateral wetlands, either to reclaim land for building or farming, or to protect against flooding. In this way, dykes and tidegates have often isolated the main river from its tributaries. These wetlands played a vital role in the production of eels, which were then able to colonise the entire catchment area. Hence the need not to put all your eggs (or rather fry) in the same basket and to disperse at least some of them to more favourable areas where the glass eels will be able to thrive in the absence of intra-specific competition.
Efforts made by the fishing industry to minimise its impact on the population throughout Europe and the numerous restocking projects undertaken in Europe and financed by public funds are at least partly responsible for the large flows of glass eels currently being observed. Those who have experience of studying these fisheries have no hesitation in saying that the abundances observed are of the same order of magnitude as those seen in the 1980s.
All that remains now is to ensure that these glass eel flows are well hosted. Restocking, or rather transferring them to more suitable areas (in the same or another catchment), is a coherent solution for speeding up this restoration.
This is where the role of professional fishing comes into its own: producing locally and managing as effectively as possible in a context of global change.