Bluebreast darter

Distribution

This darter’s range covers most of the Eastern Highlands in the US, extending latitudinally from Tennessee to New York and longitudinally from West Virginia to Illinois. Populations have historically inhabited streams in the Ohio River drainage, the Alleghany River basin , the Wabash River basin , and the Tennessee River basin . Its habitats in these regions have patchy distributions as a result of habitat degradation and fragmentation following the post-Pleistocene dispersal. In New York, its conservation status will likely be raised to ‘endangered’ following its severe population decline. Likely causes of decline have been linked to physical effects, such as impoundments, and chemical effects, such as agriculture drainage runoff, to the darter’s natural habitat. In addition, its specialized habitat makes it highly vulnerable to environmental and anthropogenic pressures. As a result of these pressures, populations have become increasingly isolated and restricted to moderate to large streams with turbid flow and high water quality.

Habitat

This darter's habitat is highly specialized and dependent on water quality and stream velocity. These habitats are located in eddies and riffles behind boulders in large to moderately sized, gravel-bottomed streams. More specifically, populations often exist in the benthopelagic regions in the water column, ranging from depths of 10 to 30 cm. Its diet typically consists of insect larvae due mostly to morphological restraints, including an average gape size of around 8 mm. Temperature ranges year-round are unknown, but spawning water temperatures range from 10 to 24 °C. Predators for this particular species are not clear, but data on a sister species, the rainbow darter , suggest larger freshwater fish, such as burbots , stonecats , and smallmouth bass have been known to prey on darters. Although data are largely unknown, predation effects on the bluebreast darter are thought to be relatively low due to the small, localized habitats of this species in riffles and eddies behind boulders that prevent larger pelagic fish from exploiting them. Typical anthropogenic effects detrimental to their ecology include strip mining, mica shale siltation, impoundments , and agricultural drainage runoff.

Evolution

The breeding season for this fish peaks from mid-May through June for many habitats. During this time, nuptial males develop their characteristic blue breast and brick-red spotting on their sides. Spawning begins when the males become territorial and seek out eddies and riffles in the head streams. Females soon follow and decide both the location of the reproductive event and the individual mates. Mating is stimulated once the female begins a ritual that involves a sequence of erratic darts that are then mimicked by the male. Once this occurs, the female will bury herself into a gravel shoal, nearly level with the bottom of the streambed. Then the male will approach from above and a series of vibrations, lasting no longer than 10 sec at a time, will signify each reproductive event. This is known to occur at least three times per reproductive event. About 100 eggs are laid during this time. The males then stay behind to guard the eggs during a seven- to 10-day incubation period, after which parental care ceases. Data on clutch sizes are unclear for ''E. camurum'', but studies on sister species, like the fantail darter , suggest numbers range from 33 to 96 individuals. Sexual maturity for the juveniles is reached within the first year for most species within the genus, and the typical life span for ''E. camurum'' is three years. Anthropogenic changes in water velocity can affect its breeding cycle . Also, increased turbidity due to stormwater runoff in streams can be detrimental to egg clusters buried in the gravel streambed, often causing eggs to become detached and free flowing, downstream and out of the protective care of the male.