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Few studies carried out on the Giant Pearl Mussel, the specie and its vital needs are still unknown to science. It is therefore difficult to state with certainty on the reasons of its fast decline.
Many factors can however be identified as possible disruptors of its health:
  • The near disappearance or the shortage of host fishes, important actor of the mussels’ reproduction : the European Sturgeon and the Freshwater blenny for the southern populations.
  • The deterioration of sediments and the destruction of habitats : pollution, canalizations, dredging, and extraction of aggregates but also the silting due to human activities: impacts of the intense agriculture, or of the dams on the quality and quantity of sediments as well as on their transit.
  • Overfishing: From the 18th to the 20th Century, the Giant Pearl Mussel was fished for its mother-of-pearl and commercialized for the production of cufflinks or knife handles.
  • The fragmentation of populations: the absence of ecological continuity leads to a genetic impoverishment that can lead to a loss of biodiversity.
  • Impediments (dams and sills) prevent the free circulation of migrating fishes and sediments, reduce the speed of the water and destroy the habitat upstream of rivers by siltation and downstream by the erosion of the soils.
  • Water pollution: the Agricultural or industrial activities can lead to polluting discharges and move to rivers and can be toxic for Margaritifera auricularia.
  • Climate change : The expecting effects of global warming are the reduction of water flows and the warming of the water, which would increase the effects of eutrophication in summer (increase of the vegetal production) and the dredging, two causes of the destruction of habitats.
  • The invasive species introduced such as the primrose willow or the zebra mussels, both harmful for the Giant Pearl Mussel development and potentially other species could be carriers of diseases for the Giant Pearl Mussel.

Studies and censuses have been carried out on different stations where parts of the population of Vienna and Creuse are located. They reveal a reduction of the livestock of about 60% on the last 10 years, and until 95% on some stations. This decline increased drastically over the last three years even though the causes of its disappearance remain unknown. It therefore leads to the emergency of studying the specie in order to be able to act for its protection and for the restoration of its habitats.