116 Lynn B. Starnes and Arthur E. Bogan 



gradient in the headwaters. Elevation changes in Little South Fork are 

 shown in Figure 2. Above Parmleysville (Sta. 4), where 12 species occur, 

 there is a relatively rapid decline in species diversity. The last species 

 encountered as we progressed upstream (Sta. 2) were Villosa taeniata 

 and V. trabalis, with all species absent at Station 1, 11 km above Sta- 

 tion 4. In the headwaters above Mt. Pisgah there is an average gradient 

 of 3.75 m/km; below this area it decreases to 1.2 m/km. The abrupt 

 change in stream gradient with associated physical changes is an effec- 

 tive faunal barrier (Fig. 2), as noted by Masnik (1975) for fish in the 

 upper Clinch River system. From the headwaters to the river area just 

 above Mt. Pisgah there is a faunal transition zone: gradient sharply 

 decreases, substrate shifts from boulder and bedrock to cobble and 

 sand, and river velocity decreases. 



The section of the river at Mt. Pisgah is apparently a major physi- 

 cal barrier to naiad distribution farther into the headwaters. Similar 

 distributional limitations have been noted in other Tennesseee River 

 tributary streams. Apparently at and above this section of the river, the 

 unionids are not able to become established for any of several reasons: 

 change in fish fauna (lack of suitable host fish), lack of suitable sub- 

 strate, lack of nutrients, and thermal fluctuations. The observed faunal 

 barrier above Mt. Pisgah was anticipated by the work on unionid dis- 

 tribution in the headwaters of the Tennessee River by Stansbery (1972), 

 Stansbery and Clench (1974, 1975, 1978), Ahlstedt and Brown (1980), 

 Ahlstedt (1982), and the work on fish distribution by Masnik (1975). A 

 similar increase in stream gradient and corresponding faunal changes 

 was also observed in the Little River, Blount County, Tennessee (Bogan 

 and Starnes 1982). The small assemblage of species found in the rivers 

 just below the zone of increased gradient is one typical of small streams 

 (e.g., Lasmigona holstonia, Medionidus conradicus, Villosa iris, V. taen- 

 iata, Pleurobema oviforme, Alasmidonta viridis). 



Current surface coal mining regulations (Kentucky Permanent 

 Regulatory Program, and the Surface Mining Control and Reclamation 

 Act of 1977) are designed to protect aquatic resources. However, even if 

 roads and silt control structures are properly designed, constructed, and 

 maintained, we are uncertain as to the survival of sensitive unionid 

 populations. Multiple mines, whose impacts on the watershed will be 

 combined or cumulative, characteristically will locate within coal-rich 

 watersheds. To preserve water quality and protect the unionid fauna, 

 the number of permits issued within both Little South Fork and indi- 

 vidual tributaries should be limited, and an annual monitoring program 

 to evaluate the status of the unionid populations should be initiated. 

 Survival of this river's unionid fauna possibly will be directly related to 

 compliance with and enforcement of the Act by inspection and 

 enforcement personnel of Kentucky and the Office of Surface Mining. 



