The orangefin darter (Etheostoma bellum) is a species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is found in Barren River and Green River systems in Tennessee and Kentucky. This moderate-sized fish usually matures between one and two years of age. The territorial males spawn over the top of buried females in the gravels of fast-flowing riffle areas. This usually occurs from late April to late June. Both the juveniles and adults are vicious predators, and mainly like to feed on dipteran larvae. Distribution These darters are known only from the Green and Barren River watersheds. The Green River is the largest river of the two, and the Barren River is a tributary to the Green River, which is known for a "biodiversity hotspot." This river's hotspot is considered to be between the 100-mile stretch from Green River reservoir dam and Mammoth Cave National Park. More than 150 fish species and 70 mussels have been found in this system, and many other aquatic species. This river drains to the Mississippi, but the orangefin darters do not go that far down the system. Green River is a flowing system with many waterfalls, and mountain springs flowing into it to give a clean green look because of the depth. The Barren River headwaters are more in Tennessee, but flows in Kentucky, also. The Barren River is north of the Nashville Basin, in Clay, Macon, and Sumner Counties, draining the northward-sloping portion of the Highland Rim. It meets the Green River around Warren County, Kentucky. "A typical Highland Rim stream is cool, clear water, gravel substrates, and riffle pool habitats." Ecology The upper Green River system was studied, and six endemic darter species were analyzed. Over 300 sites were examined during a 13-year period with five classes in the landscape map: agriculture, forest, water, and developed/exposed. "Orangefin darter was detected at 46% of the sample sites and occupies portions of all major river systems in the watershed." This darter occurred more often than the other five darter species, but it was mostly around forest-covered areas or below large reservoirs. It also was found around fine-loamy soils that had good water velocity, and averaging low 50-degrees temperatures. This species needs the right living environment to feed and spawn, but in these living areas are predators, and competition occurs.