the middle and upper Tennessee River drainage in Tennessee, Alabama, Georgia, North Carolina, Virginia, and Mississippi It has also been reported in scattered collections in Bear, Barren Fork, Second, and Shoal creek systems, which are all tributaries of the Tennessee River The extent of the occurrence is approximately 20,000 square kilometers Ecology The blueside darter thrives in benthopelagic freshwater systems Their preferred habitat is in rocky pools and adjacent riffles of clear creeks and small fast rivers with sand and gravel substrate and moderate gradient, and commonly in slow to moderate flow, in shallow margins of pools and runs, as well as n streams characterized in general by moderate to swift flows. The differences in substrate are dependent upon depth and movement of water so it is difficult to determine whether substrate or water flow is a defining characteristic in habitat choice A study completed by Schilling in 2009 conveyed that blueside darters seemed to maintain a fairly shallow depth in the water column with a maximum depth of 60 cm. Due to the seasonal variations in the regions where blueside darters occur, temperatures vary depending on the time of year and do not limit micro-habitat selection The Schilling experiment also indicated that the blueside darter did show tolerance to conductivity changes with an average pH for micro-sites being slightly basic which is indicative to limestone rock substrate. Populations have been relatively stable in most areas where the blueside occurs however, in a few areas scientists have noted a downward trend in population sizes Anthropogenic factors that may be to blame for this decline are water pollution, run-off from agriculture, and siltation Life History Most darters have specific habitat requirements regarding substrate composition, water velocity, and water depth Harrison (2004) suggested that darters have specialized reproductive behaviors which may make suitable spawning habitat limiting factor. The blueside darter spawns once a year when water temperatures reach 21° - 23 °C roughly during March through May throughout the range however in TN spawning starts between mid-February and mid-March with reproduction occurring April to early May Spawning occurs in deeper riffles than those used by Etheostoma stigmaeum. Female blueside darters show increased fecundity as they grow longer in length. At 1 year of age large females are sexually mature but there is limited data on male sexual maturity Darters have two spawning behaviors; they either bury the eggs in the substrate or