Wounded darter

Wounded darter
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Percidae
Genus:	Etheostoma
Subgenus:	Nothonotus
Species:	E. vulneratum
Binomial name
Etheostoma vulneratum (Cope, 1870)

The wounded darter, Etheostoma vulneratum, is a small freshwater fish in the family Percidae. It is one of 324 fish species found in Tennessee, and is a member of subgenus Nothonotus.

The wounded darter is a small percid fish characterized by a large caudal peduncle (like other members of subgenus Nothonotus), a terminal mouth, lines running the length of its body, a rounded caudal fin, eyes oriented nearly vertically, and olive coloration. Upon reaching sexual maturity, the male is dotted with small red spots with medial fins containing red blotching.^[2]

The species occurs in cool- to cold-water streams and is restricted to the Tennessee River and Little Tennessee River systems.^[3] E. vulneratum has not thoroughly been studied scientifically, and as a result very little literature exists on the ecology and lifecycle of the species. However, many of the other 19 recognized species within its subgenus, Nothonotus, have been studied in greater detail, and some assertions made about E. vulneratum are merely assumptions based on the similarities of the species within the subgenus.^[4] Phylogenetics suggest its most genetically similar relative is the more heavily studied boulder darter, Etheostoma wapiti.

Due to habitat degradation and other human-induced pressures, the wounded darter is struggling in much of its range.^[5] E. vulneratum is a known host for the glochidium stage of some freshwater mussels.^[6] The darter is drawn to a specialized lure organ on the mussel, which excretes a large volume of glochidia upon contact with the fish. The glochidia then attach to the gills where they begin early larval development.

Distribution

The wounded darter occurs throughout much of the upper Tennessee River drainage, north to far western Virginia.^[7] The westernmost extent of its distribution is White’s Creek, on the eastern slope of the Cumberland Plateau in Tennessee, with its southeastern terminus of its distribution being the Little Tennessee River in North Carolina above Fontana Dam. The species is most abundant in reaches of the Little River in Blount County, Tennessee, as well as localities in the Little Tennessee River and the Clinch River above Norris Reservoir.^[8] Throughout the majority of its range, however, E. vulneratum is not as common. Surveys suggest this species is struggling throughout much of its range.^[9]

Historically, the wounded darter was more widespread within the upper Tennessee River drainage. Due to anthropomorphic pressures, including the creation of impoundments, this darter, as well as other darter species, can no longer inhabit many stretches of its native creeks and rivers. In addition, agricultural practices of the 1900s have left many of these streams unsuitable for this darter’s reproductive and habitat needs. Today, the wounded darter is restricted to the uppermost reaches of rivers and rivers that have not been impounded.^[10]

Ecology

The wounded darter inhabits moderate to large rivers. Its preferred habitat is boulder or coarse rubble and cobble, often with overhanging ledges. Their habitat, also including rock piles, provides optimal resting, hiding, and nesting areas.^[11] Unlike many similar darters, E. vulneratum is associated with gentle to moderately flowing water, as opposed to swift currents and riffles. It occupies depths of 0.5 m or more where suitable habitat exists.^[12]

During winter months, the wounded darter’s diet consists of about 90% midge larvae, including chironomids. Their diets change as temperatures increase, diet shifts to 70% midge larvae with the rest being mayfly nymphs, water mites, larval black flies, crane flies, and hydropsychid caddisflies.^[13]

Several predatory piscivorous fishes commonly prey on the wounded darter. These include centrarchids and percids such as Micropterus dolomieu and Perca flavescens, respectively, among others. The primary competitors of the wounded darter are other darters of the Etheostoma and Percina genera. In addition, any benthic insectivorous fish, such as sculpin, may compete with E. vulneratum for food and habitat resources.^[14]

Lifecycle

A study of E. vulneratum in the Little River in eastern Tennessee indicates the wounded darter begins spawning in May when water temperatures reach 16°C. Breeding continues until late July or later, when water reaches 20°C.^[15] Females deposit eggs in clutches in cavities on the undersides of rock ledges or slab rocks supported by other rocks. Nests contain an average of 48 eggs, but have been observed to contain 17 to 166 eggs. These eggs, though deposited in one nest, can result from multiple spawning acts, possibly with multiple females contributing. Spawning can occur multiple times in one breeding season. Occasionally, as the female deposits her eggs, the male stands guard outside the nesting cavity and returns later to fertilize them. He then guards the eggs until they hatch. In one study, one male E. vulneratum guarded a nest for 17 consecutive days, perhaps more a behavior of territoriality than parental care.^[16]

Upon hatching, the benthic larvae are largely immobile and defenseless until the absorption of their yolk sac. At one year of age, lengths of E. vulneratum range from 22 to 40 mm. Similarly to Etheostoma maculatum, sexual maturity is not reached until age two, with a lifespan of around four to five years.^[17]

Management

Due to the current abundance of E. vulneratum, it does not warrant protected status. Because of the rarity, jeopardized status, susceptibility to ill effects from contaminants, and restricted ranges of its sister species, the wounded darter could easily become an imperiled species and should be monitored periodically.^[18]

The biggest contributing factor to the decline in wounded darter numbers is habitat loss from the creation of impoundments. With fear of localized extirpation of E. vulneratum from hydroelectric dam projects on the Little Tennessee and Cheoah Rivers, the utility company Tapoco commissioned a restoration project for the wounded darter in 2008.^[19] Soon after, Knoxville, Tennessee, the nonprofit Conservation Fisheries, Inc. (CFI) began propagating wounded darters for eventual reintroduction. In addition to wounded darters, the restoration project included the stonecat (Noturus flavus) and the sicklefin redhorse (Moxostoma spp.).^[20]

CFI’s captive propagation process involves collection of wild adults, captive spawning, hatching, rearing, tagging and releasing. This protocol has been refined by CFI since 1995 through propagation of the wounded darter’s sister species, the boulder darter. Nearly 900 young of wounded darters were reintroduced into the Cheoah River between 2008 and 2009, with similar numbers being reintroduced annually to date. CFI continues to survey for wounded darters in the Cheoah River, as well as other rivers in the Tennessee River and Little Tennessee River drainages.^[21]

Recommendations

To ensure the long-term viability of current wounded darter populations, it is essential to curb anthropogenic stressors that affect the species. To accomplish this, current habitat must be preserved or improved throughout the range of the species.^[22] Dams or other impoundments should not be built in rivers where the wounded darter exists, as they alter stream habitat, nutrient loads, and trophic characteristics to such a degree that it becomes uninhabitable for many stream-inhabiting species.^[23] In addition, halting of point-source pollution, such as industrial effluent drains, which lead into waterways occupied by the wounded darter should be prohibited.

Maintaining intact riparian zones will aid in protecting stream quality. Riparian foliage helps to maintain stream banks, slowing the rate of erosion, as well as remediating nonpoint-source pollution, including runoff from roadways and agriculture. This runoff can contain potentially harmful substances such as petroleum, pesticides, herbicides, polychlorinated biphenyls, fertilizers, and sediment.^[24] Furthermore, fencing large livestock from rivers inhabited by the wounded darter will reduce the threat of sedimentation and substrate alteration.

Monitoring of E. vulneratum should implement noninvasive monitoring techniques pioneered by CFI. These techniques differ from traditional fish monitoring methods (gill and trammel nets and shocking that tend to yield high rates of mortality due to harm caused to the fish). Instead, sampling techniques such as visual monitoring and seine surveys should be used.^[25] When streams are monitored, specific localities containing suitable wounded darter habitat should be selected. They should be surveyed once per season to reduce bias if the fish move to various microhabitats in response to the changing of seasons.

References

Further reading

• http://www.bio.utk.edu/hulseylab/Fishlist.html
• "Habitat use of etheostoma maculatm (spotted darter) in Elk River, West Virginia" Osier and Welsh, 2007
• "Etheostoma (nothonotus) wapiti (osteoichthyes, percidae), a new darter from the southern bend of the Tennessee river system in Alabama and Tennessee" Etnier and Williams, 1989
• "Systematics of the Percid Fish, Etheostoma maculatum. Kirkland, and Related Species of the Subgenus Nothonotus" Zorach and Raney, 1967
• "Life History and Comparative Ecology of the Sharphead darter, Etheostoma aucuticeps" Bryant, 1979
• "The comparative ecology of three species of Nothonotus in Tennessee's Little River" Styles, 1972
• "The American Darters" Kuehne and Barbour, 1983