Cyprinella venusta

Introduction

The following is a description of a proposed monitoring plan for the blacktail shiner. The common name of Cyprinella venusta is the blacktail shiner. It is one of the 324 fish species found in Tennessee.^[1] The blacktail shiner is a somewhat slender minnow with 8-9 rays on the anal fin, and a prominent black spot at the base of the tail fin.^[2] The back is usually yellowish-olive, and the sides are silvery with hints of blue. Adults usually reach 4 inches in length. Blacktail shiners are found in the southern United States west of the Appalachian Mountains.^[3] The species ranges east and west from north central Florida to West Texas, and north to southern Illinois. C. venusta is most common in pools and runs of clear, sandy-bottomed, small to medium rivers, typically in areas with sparse vegetation and strong current, but upland populations occur in creeks over substrates with more gravel and rubble^[4][5] Populations in the western part of the range are often in turbid water. Eggs are deposited in crevices. Spawning is from late March to early October, and is most intense from April to early September.^[6] Females reach sexual maturity at 42 mm and may produce clutches numbering from 139-459 eggs, which measure 0.97 to 1.34 mm in diameter.^[5] Currently, this species is of relatively low conservation concern and does not require significant additional protection or major management, monitoring, or research action.^[7] The areas where C. venusta have been most successfully collected have been impoundments, large rivers, and large streams in swift chutes below riffles. Currently, blacktail shiner populations are stable but some issues for concern may be habitat changes associated with flood control projects, siltation from development sites, deterioration of water quality, and recent water draw down for mining and irrigation, therefore suggestions on the mitigation of the effects of these disturbances are recommended.^[8][9]

Geographic Distribution of Species

C. venusta occurs in the Gulf drainages from Suwannee River, Georgia and Florida, to Rio Grande, Texas; Mississippi River basin (mostly on Former Mississippi Embayment) from southern Illinois to Louisiana and west in Red River drainage to western Oklahoma.^[5] Blacktail shiners are found in the southern United States west of the Appalachian Mountains. The species ranges east and west from north central Florida to West Texas, and north to southern Illinois. In Texas, blacktail shiners are unknown in the Panhandle, being found primarily from the Edwards Plateau eastward. The blacktail shiner has also been found from the Rio Grande basin in Texas, east to the Suwanee River, and north through the Mississippi River basin to the confluence of the Ohio River. Two of the three recognized sub-species occur in Alabama.^[10] The slender blacktail shiner, C. v. stigmaturus, is found in the upper Mobile basin (most frequently above the Fall Line), while the eastern blacktail shiner, C. v. cercositgma, occurs in the lower Mobile basin and coastal rivers draining the state. Intergradations between these sub-species have been recognized in the Alabama, Cahaba, and Tallapoosa river systems.^[11]

Ecology

C. venusta has a large, black caudal spot which distinguishes it from most other minnows. The caudal spot of C. venusta may be faint, especially in populations inhabiting turbid waters, and they could likely be confused with C. lutrensis (red shiner); however C. lutrensis has 9 anal rays (versus 8) and usually 35 or fewer lateral scales (versus 36 or more). C. venusta hybridizes with C. lutrensis in Texas,^[12] and in Illinois.^[13] C. venusta is an invertivore (feeds on invertebrates). Its diet includes algae, seeds, aquatic and terrestrial insects. Aquatic insects and algae were the most common food items of C. venusta in the Blanco River, Texas; sediment and detritus were found in 21% of the 36 guts examined ^[14] C. venusta feed primarily during the day. C. venusta may serve as major food resource for piscivorous Micropterus punctulatus (spotted bass), during the summer, in Village Creek (Neches River), Texas.^[15] Blacktail shiner macrohabitat is small to large-size streams. Blacktail shiner mesohabitat is ubiquitously distributed among pools, runs, and riffles with silt, gravel, and bedrock substrates. In the Blanco River, Texas, C. venusta was most abundant in swift runs in the spring and summer.^[14] Species occurred throughout the year in riffle and sandbank habitats, in Village Creek (Neches River), Texas. During summer, greatest number collected from sandbank habitats; also found in deep channel and riffle habitats, though none >47 mm (1.85 in) occurred in riffles. Individuals <17 mm (0.67 in) were found predominately in riffle habitats, during fall and winter. Juveniles occurred almost exclusively in sandbank mesohabitat, during spring.^[15] C. venusta are commonly found in sandy or rocky areas of Lake Texoma, Oklahoma-Texas, generally in clearer water of the downstream area; occasionally abundant in the tailwaters, and rarely found in the headwaters. Currently, blacktail shiner populations are stable but some issues for concern may be habitat changes associated with flood control projects, siltation from development sites, deterioration of water quality, and recent water draw down for mining and irrigation, therefore suggestions on the mitigation of the effects of these disturbances are recommended.^[8][9]

Life History

The lifespan of the blacktail shiner is up to 4 years in the Leaf River system, Mississippi and up to 5 years in the Blanco River, Texas.^[14] C. venunsta spawning season is April through September, in Texas.^[14] In Mississippi, late March – early October, with most females reproductive from April- early September.^[16] According to Moriarty and Winemiller,^[15] in Village Creek (Neches River), Texas, C. venusta revealed size distribution patterns consistent with a protracted spawning season. Prime spawning habitat for the blacktail shiner is in fractional crevices; generally located in flowing water, preferring crevices in current velocities of 0.30 m/s (1.00 ft/s).^[17] Populations in reservoirs shifted their preference of current velocity, choosing crevice sites in locations of much lower current speeds.^[17] In the Blanco River, Texas, C. venusta were observed depositing eggs underneath small boulders and large cobble in a bedrock riffle in the swiftest current velocities available. Males respond to sounds produced by spawning females and are able to distinguish these sounds from those produced by related female red shiners. Males are territorial, defending a crevice from other males. Breeding pair swims along the crevice, the female deposits eggs; usually the sperm has already been released into the crevice, so the eggs are deposited into a crevice with viable sperm. Immediately after spawning, the male doubles back and eats any eggs that failed to make it into the crevice. Small males (sneakers) try to fertilize eggs by darting between the dominant male and spawning female. Both large and small males will enter another male's territory and deposit sperm in a crevice before the male courts a female to lay eggs in the crevice.^[6] A female blacktail shiner can have up to 340 ova, from the Blanco River, Texas.^[14] In southwestern Mississippi, clutch sizes ranged between 139 and 459 ova in females 48.6-72.0 mm (1.91-2.83 in); average mature ovum diameter was 1.15 mm (0.05 in); ovaries in mature females constituted 5.8-19.1% of the somatic body weight.^[6] Females from the Pearl River, Mississippi, spawned 20-46 clutches during the reproductive season.^[17] The size of sexual maturation is between 32 mm (1.26 in) and 42 mm (1.65 in).^[6] In the Leaf River system, Mississippi, average length was 24 mm (0.94 in) for age 1, 46 mm (1.81 in) for age 2, and 72 mm (2.83 in) for age 3; populations consisted mainly of age classes 0 and I^[17] In the first year, C. venusta reaches about 45–60 mm (1.77-2.36 in).^[17] Average length was 45 mm (1.77 in) for age 0, 66 mm (2.60 in) for age 1, 90 mm (3.54 in) for age 3 and older in the Blanco River, Texas.^[14]

Current Management

Currently, this species is of relatively low conservation concern and does not require significant additional protection or major management, monitoring, or research action. The areas where C. venusta have been most successfully collected have been impoundments, large rivers, and large streams in swift chutes below riffles. Currently, blacktail shiner populations are stable but some issues for concern may be habitat changes associated with flood control projects, siltation from development sites, deterioration of water quality, and recent water draw down for mining and irrigation, therefore suggestions on the mitigation of the effects of these disturbances are recommended.^[8][9] Activities such as construction and operation of hydroelectric facilities, flood control, additional irrigation diversions, bank stabilization, oil and gas drilling, mining, grazing, stocking or introduction of nonnative fishes that the Federal Government carries out that may jeopardize the continued existence of C. venusta. Another potential impact on the population could be hybridization. C. venusta competes with C. lutrensis for breeding grounds and food resources. C. venusta hybridizes with C. lutrensis in Texas,^[12] and in Illinois.^[13]

Management Recommendations

The blacktail shiner is a common baitfish used for sport fishing so they can be managed for sport fish bait as well as for non-economical reasons. A mark/recapture method of monitoring C. venusta will be performed during the breeding season, (depending on location) once a year, when the fish are most active and therefore ensuring the success of the sample. The areas where C. venusta have been most successfully collected have been impoundments, large rivers, and large streams in swift chutes below riffles. The ideal location would be where there is a healthy native population such as the Mississippi River basin or the Suwannee River in Georgia. A 4 ft x 8 ft "Common Sense" minnow seine with 1/8 inch mesh would be ideal to collect the fish; performing about 30 seine hauls.^[18] A Visible Implant Elastomer (VIE) will be used to mark the individuals so they can be easily identified when recapturing them. VIE’s use colored fluorescent elastomer material that is injected into tissue with a hypodermic syringe. The material then cures into a pliable, solid well-defined mark, which fluoresces under blue light. The biological data will be recorded to measure survival from year to year.

References