Larger freshwater fish prey on darters, such as catfish and smallmouth bass. Intraspecific competition occurs because small invertebrates are more abundant during different times of the year, and breeding areas become a challenge, also. Darters tend to feed on small fish larvae, which adds more competition within the species. Interspecific competition can be caused by abundance of predators, or human impacts on the environment. Increasing agriculture and deforestation, or sending more pollution down the stream, can reduce the abundance of this species. The building of dams can slow the flow of water, which will have a major effect on the orangefin because they use rocky substrates and swift-moving riffles for hiding and feeding. Their ecosystem must stay balanced in the future, or stress on these endemic species can cause extinction sooner. Life history N. bellus is a moderate-sized darter of the subgenus Nothonotus, endemic to the Green and Barren River system in south-central Kentucky and north-central Tennessee. "Spawning was from late April to late June in gravel substrates of fast flowing riffles." Darters mostly inhabit somewhat deeper water until the spawning period begins, and they become more aggressive with the warmer waters. During this period, they move to better-flowing waters with riffles and rocks. When breeding starts, the territorial males, or larger mature males attract the females to come spawn. Coloration in the males is a big part also in breeding, and the "females prefer conspecific over heterospecific coloration, and prefer a particular color variant within species." When the female picks the right male, she buries herself in the substrate on his territory. The male lies parallel with her where he ejects his sperm into the substrate, so it can meet with the eggs she has laid. They lay clusters of eggs, around 60-100, but only so many will hatch within 7–9 days in 23 °C water. The male guards the nest for a few days, but finally leaves, and the eggs that hatch are on their own. Maturity is reached in a year to two, and males seem to mature sooner, and their lifespan is about five years. Their diet is mostly hydracarinads, ephemeropteran nymphs, and dipteran larvae, but it changes some depending on the time of year. They also reached their feeding peak during the afternoon, and juveniles and adults mostly fed on the same food types. Usually, the juveniles stay in the shallow waters for a while,