Many of the pocketbooks remain in the same location for their entire lifetime if the environmental conditions are favorable, but they can move a limited distance by extending and contracting their muscular foot. Sandbars may show the marks of a mussel moving to deeper water to avoid being killed by drying, high temperatures, or perdition. The movement of a mussel is slow and tedious. It can be compared to a person trying to pull a camper trailer through the forest without the aid of a vehicle. Mussels breathe by taking in water through the incurrent siphon into the mantle cavity and passing it through tiny pores into small water tubes within the gills.
Gas exchange occurs within the gill tubes and on the outer tissue surface.
From the gills the water passes to the suprabronchial chamber then out the excurrent siphon. Mussels also feed by bringing water through the incurrent siphon and passing it over the gills. Then food particles are trapped in mucous secreted by the gills. Digestion occurs in the stomach, and waste passes from the anus to excurrent siphon and out of the shell. The Fat Pocketbook is mostly found in mud, sand, or gravel bottoms of slow flowing streams and rivers.