''Potamilus capax'', the fat pocketbook pearly mussel or fat pocketbook, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

freshwater mussel Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves. The majority of species of bivalve molluscs ...

, an aquatic

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Unionidae The Unionidae are a family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids. The range of distribution for this family is world-wide. It is at its most divers ...

, the river mussels. The fat pocketbook is a large freshwater mussel which requires flowing water and a stable base on which the organism can live. However there is still inconsistent research when deciding which habitat the fat pocketbook prefers, but most likely it is a mixture of sand, silt and clay. There is nothing particularly unique about this freshwater mussel it acts very similar to other native freshwater mussels. The freshwater drum was tested in comparison to the fat pocketbooks reproductive cycle and it has proven not to differ from other freshwater mussels. They can now be found or come across in a small, undredged portion of the St. Francis River in St. Francis County, Arkansas. Greater risks that caused the population of the fat pocketbook to decrease in the past are navigation and flood control. The species seems to have cleared out of the Mississippi River where they used to be spotted, due to the river being impounded for navigation and is dredged routinely to uphold a nine- foot navigation channel. A similar situation took place in the St. Francis Floodway. Also in the White River in Arkansas the shifting sand bars no longer supply a stable substrate for the mussels. Their population is believed to be declining more currently due to canal repair activities, alterations in temperature, water flow, and impoundments remain a huge threat to the very existence of this species.

References

* Fish and Wildlife Servic

* EPA: Pesticides Endangered Species Protection Progra

Molluscs of the United States capax ESA endangered species Taxonomy articles created by Polbot {{Unionidae-stub