The mussel then expels the glochidia into the face of the unsuspecting fish, thus enabling the glochidia better position to attach to the gills or fins. The glochidia have tiny bean or spoon shaped shells that attach to the host fish. They encyst themselves and live off of the fish for a period of 1 to 25 weeks. This attachment, however, does not harm the fish. Those glochidia that don't encounter a host fish does not survive they sink to the stream bed and die.
Some species are host-specific, while others can utilize a wide variety of fish.
While attached, glochidia change form and begin to resemble adults. When the juvenile has developed a shell and is large enough to survive on its own, it then breaks free from its host and drops to the stream bottom. Wherever it drops is the area in which it will live out the rest of its life. Therefore, reproduction success depends upon an abundance of suitable host fish to complete their larval development and to increase their range. Historical Importance of Mussels Mussels have always been-and continue to be an important food source for muskrat, minks, raccoons, otters, fish, and some birds such as herons.