1 UPPER MISSISSIPPI RIVER MUSSEL SPECIES ACCOUNTS

Mussel species present and historic distribution, and relative abundance were determined for the Upper Mississippi River (UMR) and Illinois River by navigation pool. Also included were the lower Minnesota and lower St. Croix rivers. Species were designated as Rare, Common, Abundant, or as historically occurring. For the most part, species listed as rare comprised < 2 % of the community within a particular pool for most studies. Common species ranged in relative abundance from approximately 2 to 15 % however, if a species was consistently on the low or high end of this range among studies it may have been designated as rare or abundant, accordingly. Common species could be abundant in one or two surveys but rare or common elsewhere within the pool. For the most part, abundant species were reserved for the dominant species in most surveys within a given pool. Species designated as historic have not been reported live within the past ~25 years and may also be the result of recent collections of sub-fossil specimens. Data were gathered from peer-reviewed literature, technical reports, gray literature, raw survey data, personal communications, museum holdings, and state and personal databases (see Bibliography). Historically, 53 mussel species have been documented from the Upper Mississippi, Illinois, lower Minnesota, and lower St. Croix rivers (Table 1). The mussel species accounts below briefly summarize species distribution and abundance. Also listed are known migratory fish hosts (non-migratory fish hosts not listed) (in part, this project was undertaken as an attempt to identify locks and dams, which if given fish passageways may benefit disjunct mussel populations by allowing easier fish passage among pools)