New York Natural Heritage Program
Eastern Pearlshell
Margaritifera margaritifera (Linnaeus, 1758)
Bivalves

Threats [-]
The single most important cause of the decline of freshwater mussels during the last century is the destruction of their habitat by siltation, dredging, channelization, impoundments, and pollution. A healthy fish assemblage is critical to viable mussel populations and dams have resulted in heavy losses of mussels, mainly due to elimination of host fish species. Erosion due to deforestation, poor agricultural practices, and the destruction of riparian zones causes an increase in siltation and shifting substrates that can smother mussels. Domestic sewage, acid mine runoff, heavy metals, pesticides, and effluents from paper mills, tanneries, chemical industries and steel mills have all been implicated in the destruction of native mussel fauna. Since the Eastern Pearlshell inhabits coldwater trout streams, eutrophication has been a significant cause of its decline worldwide. In particular, mortality of adults increased with higher concentrations of nitrates in the water and lowered survival and poor establishment of juveniles was related to the amount of phosphates and calcium (Bauer 1988).

Conservation Strategies and Management Practices [-]
When feasible, the removal of impoundments in order to restore rivers to their natural flow would be beneficial since these structures negatively effect required fish host species as well as the mussels themselves. Since this species appears to be sensitive to eutrophication, actions which reduce run-off into high quality trout streams could be beneficial.

Research Needs [-]
There is still much to learn about this species, especially determination of its distribution with respect to its Salmonid host fish species. Details about habitat requirements (current speed, water depth, substrate grain size, substrate stability, water temperature, and water quality factors) also need investigation. However, Strayer et al. (1994) found that the distribution of Unionoids was not related to these typical physical habitat qualities, but instead was related to long term stability of the substrate (i.e., flow refuges) and other large-scale habitat variables such as riparian zone vegetation (i.e., grassy vs. forested). Both large and small-scale forces promoting the patchy occurrence of Unionoid mussel beds is an active area of research (Strayer et al. 2004).