The fish host species for these glochidia is also unknown. Based on life history information of closely related species, it is presumed that the brooding season is in May and June but this has not been documented. Thus, many opportunities for mussel research exist today. In the United States alone, more than forty species of mussels are now listed as endangered or threatened, and more than sixty others are being considered. Of the 297 species and subspecies recognized, eighteen species are presumed to be extinct.
Mussels are the most severely threatened group of animals.
However, some are still being harvested illegally for human consumption or to be used as fishing bait. It is also possible that recreational and commercial vessels are causing disturbance to the mussel beds by physically disturbing the substrate. In times of drought, mussels can be killed when they become stranded and exposed. This is a threat to winged mapleleafs due to hydroelectric peaking operations. These peaking operations hold back water to produce electricity more efficiently.