Threats and Conservation
Once the most abundant bivalve mollusc in ancient rivers around the world, numbers of the freshwater pearl mussel are now declining in all countries and this species is nearly extinct in many areas. The causes of this decline are not fully understood, but alteration and degradation of its freshwater habitat undoubtedly plays a central role. The negative impacts humans have on rivers and streams come from a wide range of activities such as river regulation, drainage, sewage disposal, dredging, and water pollution, including the introduction of excess nutrients. Anything that affects the abundance of the fish hosts will also affect the freshwater pearl mussel; for example, the introduction of exotic fish species, such as the rainbow trout, reduces the number of native fish hosts. Introduced species are also directly affecting the freshwater pearl mussel; the invasion of the zebra mussel (Dreissena polymorpha), which has been spread to new locations by being transported on the bottom of boats or in ballast waters, has impacted freshwater pearl mussel populations in all countries it has invaded.
The freshwater pearl mussel, which is completely protected in most European countries, has been the focus of a significant amount of conservation efforts. Measures have included the transfer of adult mussels to areas where it had gone extinct, the culture of juvenile mussels, and the release of juvenile trout, which have been infected with glochidia, into small rivers, but mainly the freshwater pearl mussel has benefited from habitat restoration projects in some areas. Due to the essential role salmonid fish play in the life of the freshwater pearl mussel, the conservation of salmon and trout is also central in the survival of this endangered freshwater mussel.
Read more about this topic: Freshwater Pearl Mussel
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