About Cyprinella venusta Girard, 1856
The blacktail shiner, with the scientific name Cyprinella venusta Girard, 1856, is a somewhat slender minnow. It has 8–9 rays on the anal fin, and a prominent black spot at the base of its caudal (tail) fin. Its back is usually yellowish-olive, and its sides are silvery with faint blue tones. Most adults reach 4 inches (100 mm) in length. This species' large black caudal spot distinguishes it from most other minnows. The spot can be faint, especially in populations that live in turbid waters, where blacktail shiners may be confused with the closely related red shiner (C. lutrensis). These two species can be told apart by traits: the red shiner usually has 9 anal rays (compared to 8 in most blacktail shiners) and usually 35 or fewer lateral scales (compared to 36 or more in blacktail shiners).
The blacktail shiner is distributed across Gulf of Mexico drainages, stretching from the Suwannee River in Georgia and Florida west to the Rio Grande in Texas. It also occurs in the Mississippi River basin, mostly within the Former Mississippi Embayment, from southern Illinois south to Louisiana, and west through the Red River drainage into western Oklahoma. The species lives across the southern United States, west of the Appalachian Mountains, ranging from north-central Florida east-west to West Texas, and north as far as southern Illinois. In Texas, it has not been recorded in the Panhandle, and is found primarily east of the Edwards Plateau. It also extends from the Rio Grande basin in Texas east to the Suwannee River, and north through the Mississippi River basin to the confluence of the Ohio River. Two of the three recognized subspecies are found in Alabama: the slender blacktail shiner C. v. stigmaturus occurs in the upper Mobile River basin, most often above the Fall Line, while the eastern blacktail shiner C. v. cercositgma occurs in the lower Mobile River basin and coastal rivers that drain Alabama. Interbreeding between these two subspecies has been documented in the Alabama, Cahaba, and Tallapoosa river systems.
Blacktail shiners feed primarily on invertebrates, and their diet also includes algae, seeds, and both aquatic and terrestrial insects. In a study of blacktail shiners in the Blanco River, Texas, aquatic insects and algae were the most common food items; sediment and detritus were found in 21% of the 36 stomachs examined. This species feeds primarily during the day. In summer at Village Creek, a Neches River tributary in Texas, blacktail shiners can act as a major food source for the piscivorous spotted bass (Micropterus punctulatus).
Blacktail shiners are most common in the pools and runs of clear, small to medium rivers with sandy bottoms, usually in areas with sparse vegetation and strong current. Upland populations live in creeks over substrates with more gravel and rubble. Populations in the western portion of the species' range are often found in turbid water. Their mesohabitat is distributed broadly across pools, runs, and riffles with silt, gravel, and bedrock substrates. In the Blanco River, Texas, blacktail shiners were most abundant in swift runs during spring and summer. At Village Creek in Texas, the species is present in riffle and sandbank habitats year-round. In summer, most individuals are collected from sandbank habitats; they are also found in deep channel and riffle habitats, though no blacktail shiners longer than 47 millimeters (1.9 in) have been found in riffles there. Individuals smaller than 17 millimeters (0.67 in) are found predominantly in riffle habitats during fall and winter. During spring, juvenile blacktail shiners occur almost exclusively in sandbank mesohabitat. At Lake Texoma, which sits on the Oklahoma-Texas border, blacktail shiners are common in the sandy or rocky downstream areas of clearer water; they are occasionally abundant in the tailwaters, and rarely found in the lake's headwaters. This species hybridizes with the red shiner (C. lutrensis) in both Texas and Illinois.
