Recent Catastrophic Decline of Mussels 



(Bivalvia: Unionidae) 



in the Little South Fork Cumberland River, Kentucky 



Robert M. Anderson, James B. Layzer, and Mark E. Gordon 



US. Fish and Wildlife Service 



Tennessee Cooperative Fishery Research Unit 1 



Tennessee Technological University 



Cookeville, Tennessee 38505 



ABSTRACT— During 1987, we sampled 16 sites in the Little South 

 Fork Cumberland River to assess the status of mussel populations. We 

 found 21 species, of which 12 were alive. Mean densities in the lower 

 one-third of the stream had declined from 2.9 to 7.5 mussels/ m 2 in 

 1981 to to 1.1 mussels/ m 2 in 1987. Moreover, we found few live 

 mussels at six other stations in this section of stream. Between 1981 

 and 1987, two species {Villosa trabilis and Pegias fabula), listed as 

 federally endangered, appeared to have been extirpated from the lower 

 one-third of the stream. Viable populations of most mussel species are 

 now restricted to the middle section of the Little South Fork. Surface 

 mining of coal has increased in the lower watershed of the Little South 

 Fork in recent years and may be responsible for the mussel decline. 

 Unlike the unionid mussel fauna, the density of the exotic Corbicula 

 fluminea has increased nearly ninefold since 1981. This increase appears 

 to be related to the general population expansion of C fluminea in the 

 Cumberland River system. 



Harker et al. (1979, 1980) reported on environmental conditions of 

 the Little South Fork Cumberland River (LSF). They considered the 

 stream to have relatively high water quality in comparison with other 

 drainages in the upper Cumberland River basin and to support a fairly 

 speciose flora and fauna. A total of 24 species of unionid mussels were 

 later identified from LSF (Starnes and Bogan 1982); one-third of these 

 species were Cumberlandian endemics, including two that are listed as 

 federally endangered, Pegias fabula (Lea, 1838) and Villosa trabalis 

 (Conrad, 1834). At the time of its discovery in 1977, this population of 

 P. fabula was considered to be the healthiest known, and LSF was 

 "perhaps the most pristine stream remaining within the entire known 

 range of Pegias in the Cumberland and Tennessee drainages" (Starnes 

 and Starnes 1980). 



Starnes and Bogan (1982), who made an extensive survey of 

 unionids in LSF in 1981, reported qualitative information for the entire 



'Cooperators are the Tennessee Wildlife Resources Agency, Tennessee Technological 

 University, and the U.S. Fish and Wildlife Service. 



Brimleyana 17:1-8, December 1991 



