Survey of the Black Warrior and Tombigbee Rivers, Alabama, for the ThreatenedInflated Heelsplitter Mussel Potamilus Inflatus, May 1993

摘要

On 19-24 May 1993, a survey was conducted at dredged material disposal areaslocated between River Mile (RM) 293.0 and RM 334.0 on the Tombigbee River and between RM 65.0 and RM 190.0 on the Black Warrior River, Alabama. The purpose was to search for freshwater mussels (Family: Unionidae), especially the inflated heelsplitter mussel Potamilus inflatus, listed as threatened by the U.S. Fish and Wildlife Service. A total of 69 locations at 28 disposal areas were searched by two divers equipped with surface-supplied air and communication equipment. Total bivalves (which included native mussels as well as the Asian clam Corbicula fluminea) ranged from 0.104 to 4.817/100 sq m. When present, mussels were collected at a rate of 0.005 to 0.241/minute. The maximum density of P. inflatus was 4.5/100 sq m collected at a rate of 0.228/minute. A total of 1,610 min (26.8 hr) were spent searching for mussels. After about 1,000 min had been expended, nine species of bivalves (the total collected) were found. Of the 63 bivalves collected during the survey, 52.4 percent were P. inflatus and 12.7 percent were Leptodea fragilis. Thick-shelled species, usually found in firmly packed gravel substratum, comprised only 19 percent of the fauna. Based upon estimates of size up disposal areas and collecting rates, the total number of inflated heelsplitters at the 28 disposal areas could be as high as 7,180. A total of 2,120 diver hours could be required to collect all P. inflatus at these disposal areas.