Freshwater mussels are among the world’s most imperilled animals and population declines have been reported globally (3). The Unionida populations of North America have experienced dramatic reductions in size, with around 70 percent of approximately 300 freshwater mussel species in decline and many now considered rare, endangered, and threatened (3). It is estimated that this species is only present in 40 percent of its historical range, and the populations that remain are fragmented. This species is likely to be locally extinct in Iowa, Kansas, New York, and Mississippi (3). Although it is not now thought to constitute a major threat to this species, the overcollection of mussels for the button industry may have been the cause of many population declines (3).
One reason for the dramatic decline of the snuffbox is the invasive zebra mussel (Dreissena polymorpha), which attaches to the shells of native mussels and can interfere with respiration, feeding, movement, and excretion (3). Another invasive species, the round goby (Neogobius melanostomus), may also threaten the snuffbox by displacing host fish, thereby reducing the likelihood of reproduction and the capacity for dispersal, particularly in an upstream direction (2). In Canadian populations, another invasive species, the common carp (Cyprinus carpio), is a threat to this species as it predates the juveniles, uproots plants, and feeds on sediment-associated fauna, which can increase turbidity and sedimentation (3), reducing the suitability of the habitat and even causing mussels to suffocate (2). Sedimentation can also be accelerated within the habitat of the snuffbox by intensive timber harvesting, heavy recreational use, and poor land use practices (2) and these actions are thought to be the primary limiting factor for most species in the Sydenham and Ausable Rivers in Canada (3).
The construction of dams is likely to affect both upstream and downstream mussel populations, by changing water temperatures, disrupting river flow patterns, scouring river bottoms and eliminating suitable habitats (2). Dams also prevent the movement of host fish in rivers, which limits the dispersal of the snuffbox and effectively isolates upstream and downstream populations (2).
The leaching of fertilisers, herbicides, and pesticides into the habitat of the snuffbox is likely to be a threat to this species and its habitat, as well as contamination from oil, grease and heavy metals which can enter aquatic areas from nearby roads (3). This pollution may directly affect the snuffbox, as well as indirectly threaten this species by reducing host fish populations, thereby reducing the chances of successful reproduction.