Endemic Darters

Forty species/subspecies of darters live in Arkansas; many of them are beautifully colored, especially males during the breeding season. Of these forty, five species are endemic to Arkansas, meaning that they occur nowhere else on the planet. Those five endemic darters are the beaded darter (Etheostoma clinton), strawberry darter (Etheostoma fragi), yellowcheek darter (Etheostoma moorei), paleback darter (Etheostoma pallididorsum), and the most recently described Ouachita darter (Percina brucethompsoni).

The beaded darter, Etheostoma clinton (named after Bill Clinton, the forty-second president of the United States) was described (elevated) by Richard Mayden of St. Louis University in Missouri and Steven Layman of Kennesaw, Georgia, from specimens collected in the upper Ouachita and Caddo rivers. It was formerly known as the speckled darter (Etheostoma stigmaeum), described in 1891 by noted Arkansas ichthyologist Seth Eugene Meek (1859–1914). The type locality is the Caddo River, 3.2 km north of Amity (Clark County), and it is endemic to the upper Caddo and upper Ouachita rivers upstream of the Fall Line in the Ouachita Mountains. Habitat for E. clinton includes clear, sandy/rocky pools of small-to-medium-sized rivers with moderate gradient and swift current. It can be distinguished from E. stigmaeum by having nine anal soft rays (vs. eight), modally thirteen to fourteen pectoral rays (vs. fourteen), nearly naked or naked cheeks (vs. usually partly scaled), and a higher mean count of lateral scales (49.9 vs. 46.4). This darter has not yet been ranked by NatureServe but does have a state rank of S2 (imperiled) in Arkansas. A study is badly needed to help clearly define the geographic distribution of the species.

Described originally in 1968 by Donald Distler (1928–2017), a Kansas ichthyologist, E. fragi was initially described as a subspecies of the orangethroat darter (Etheostoma spectabile), E. spectabile fragi. Later, it was elevated to full specific status based on a combination of meristic counts, unique color pattern in spawning males, and the absence of any intergrade populations. Taxonomically, E. fragi is a member of subgenus Oligocephalus. This darter inhabits the Strawberry River system in Fulton, Izard, and Sharp counties in northeastern Arkansas. It is part of what is known to ichthyologists as the “Etheostoma spectabile complex,” as there are a number of spectabile-like species both named and undescribed. This fish is a small darter (usually about 5 cm) with numerous saddles running across the back with ten to twelve narrow vertical bars on the sides, and it has a green anal fin, unlike very similar rainbow darters (Etheostoma caeruleum), which have red pigment in the anal fin. In addition, E. fragi has horizontal lines on the sides below the lateral line. This species has the gill membranes narrowly joined across the throat with a premaxillary frenum (bridge of flesh) present on the snout. The lateral line is incomplete with twenty-nine to thirty-seven lateral line scales present. Generally, the cheek has five or more rows of scales, while the opercle is typically more than ninety percent scaled. Dorsal spines number ten or eleven, while dorsal rays are twelve or thirteen. In the anal fin, there are two spines and six or seven soft rays.

As with many darters, the strawberry darter inhabits headwater streams in the upper portion of the Strawberry River, where it occurs in shallow, gravel riffles with slow to moderate current. Food habits and reproductive behavior of this endemic darter have not been studied. The strawberry darter has a conservation status of threatened due to its small geographic range in Arkansas and is listed S1 (critically imperiled) by NatureServe.

The third endemic darter is the yellowcheek darter, Etheostoma moorei, named after famous midwestern ichthyologist George A. Moore (1899–1999) of Oklahoma. This darter was named by Edward C. Raney (1909–1984) of Cornell University and Royal D. Suttkus (1920–2009) of Tulane University in 1964 from the type locality in Devil’s Fork of the Little Red River, which is 4 km southwest of Woodrow (Cleburne County) and 9.7 km west of Drasco (Cleburne County). It was placed in the distinctive darter subgenus of Nothonotus, but the type locality was destroyed by the impoundment of Greers Ferry Lake. Currently, the yellowcheek darter inhabits the upper Little Red River drainage above Greers Ferry Lake in Cleburne, Searcy, Stone, and Van Buren counties. This fish specifically occurs in the Little Red River and its tributaries, including Archey Creek, Middle Fork, South Fork, and Devil’s Fork, although the latter site population is thought to be highly reduced or extirpated. This darter is listed as S1 (critically imperiled) by NatureServe.

Characteristically, this is another small darter (less 7.6 cm) that has a compressed body as well as a deep caudal peduncle. The back may have eight or nine indistinct saddles, while the sides have faint vertical bars. Some dark horizontal lines may occur on the posterior portion of the body. This species has a premaxillary frenum, a scaled opercle, and a complete lateral line with fifty to sixty scales. The dorsal fin has ten to twelve spines and nine to twelve soft rays, while the anal fin has two spines and six to eight soft rays. Body coloration is slightly brown to gray, with darker brown saddles over the back and lateral bars on the sides. The posterior part of the body has dark brown or black horizontal stripes. Occasionally, males have light spots on the body. A suborbital bar is present on the head. Breeding males are brightly colored with a blue breast and throat area and light green venter. The median fins of males have thin yellow submarginal bands, a broad red-orange medial band, and a basal green band. All paired fins have a reddish orange hue. Generally, females are not brightly colored.

The yellowcheek darter occurs only in the clear, upper, swift tributaries of the Little Red River. This darter prefers gravel or rubble riffles with swift to moderate flow. Podostemum ceratophyllum (hornleaf riverweed) aquatic vegetation is often found growing in the same riffles. One recent study found evidence of niche partitioning between E. moorei and E. caeruleum in the Middle Fork of the Little Red River. Yellowcheek darters seemed to prefer cobble and gravel substrates (unlike the rainbow darter). Density dynamics of E. moorei have been studied in both drought and non-drought periods. Results were highly variable within and among streams, with the highest single riffle density of 2.1 individuals per square meter occurring at a site on the Middle Fork.

Much of the original habitat of E. moorei, including the type locality, was destroyed by the impoundment of Greers Ferry Lake in the early 1960s. This darter cannot tolerate impounded waters, but populations still live in tributaries above the lake. After the impoundment, notable declines in population numbers occurred. Seasonal drought and stream drying are common in streams of the Boston Mountain Plateau and have also undoubtedly played a role in the decline of E. moorei populations. One study conducted in 1983 provided a total estimate of 60,000 individuals for this species. Another study, done in 2001, estimated a total population of 10,300 individuals, an 83 percent decline.

A life history of this species found E. moorei feeding primarily on dipteran larvae (Chironomidae and Simuliidae), although stoneflies, mayflies, and caddisflies were also eaten. Spawning of this darter occurs from May through June and is reported to occur in the swifter portions of the riffles apparently around and under the large substrate. In laboratory observations, William D. Voiers (1923–2017) of Eureka Springs (Carroll County) confirmed that E. moorei is an egg-burier. Both males and females reach sexual maturity at one year of age, and the maximum life span is about four years. The endemic yellowcheek darter was added to the Federal Endangered Species list in 2011, after which a captive breeding program was begun at the University of Arkansas at Pine Bluff (UAPB), with the idea to reintroduce individuals where they have been extirpated.

The fourth endemic darter of Arkansas is E. pallididorsum, described originally from the Caddo River, 13.7 km west of Black Springs (Montgomery County), by Donald Distler and Artie Metcalf (1929–2016), both graduate students at the University of Kansas. This state endemic was discovered at the type locality while Distler and Metcalf were on a field trip through the Ouachita Mountains on their way to a national ichthyological meeting. Later, the paleback darter was placed into the darter subgenus Ozarka.

This small darter inhabits only the upper Caddo River and a few tiny tributaries of the upper Ouachita River in the Ouachita Mountains of Garland, Montgomery, Pike, and Polk counties. It is a small (5 cm) and slender darter, but it has a large head and a moderately rounded snout. The conspicuous dorsal stripe is olive, with the sides distinctly bicolored with the upper portion dark brown, lower side and venter orange (male) or white with black stippling (female). A wide, pale stripe extends along the middle of the dorsum from the head to the base of the caudal fin, which is often crossed by one to six poorly developed saddles. Sides have four or five indistinct vertical bars, and dark spots or stippling cover the venter and lower sides. The lateral line is straight, incomplete, and short (forty-three to fifty-five scales), typically not extending behind the base of the first dorsal fin. On the head is a prominent black suborbital bar, and a dark humeral spot is also present. The first dorsal fin has a black margin and basally. All other fins have narrow dark bands. Breeding males have bright orange bellies and a bright orange medial band in the first dorsal fin.

The paleback darter inhabits shallow pools at the margins of small gravel-bottomed, spring-fed streams. It tends to avoid any areas of moderate-to-swift current and is occasionally found associated with vegetation. A life history study of this darter found its diet to consist mostly of small crustaceans, mayfly larvae, and other immature aquatic insects. Predators include western lesser sirens (Siren intermedia nettingi), which have been reported to be feeding on these darters at a tributary of the Caddo River near Caddo Gap (Montgomery County).

Reaching sexual maturity at one year of age, the paleback darter spawns primarily in February and March. An aquarium study of the spawning behavior of this species showed that males were aggressive but non-territorial and had no elaborate courtship displays. Females may spawn more than one clutch per breeding season, and E. pallididorsum was documented to be an egg-attacher. These darters live a maximum life of two years. Hermaphroditic specimens have been previously discovered in Montgomery County. Populations of this species in the Ouachita Mountains are generally small, with an average number of four individuals taken from various sites in one research study. The paleback darter is considered threatened in the state because of its small geographical range, small population size, and specialized habitat requirements. It is listed as S2 (imperiled) by NatureServe.

The final darter is the most recently described darter in the state, the Ouachita darter, Percina brucethompsoni. For many years, this species was called Percina nasuta. However, it was elevated to specific status in 2014, based on morphological features and phylogenetic analysis of mitochondrial DNA sequence data. Percina brucethompsoni is included in the darter subgenus Swainia.

Unlike the other darters discussed, the Ouachita darter is a robust, medium-sized species (less than 10 cm) of Percina and has a long head and snout. If measured, the snout length goes into the head length 3.8 times or less while the head length will go into the standard length of the individual fish less than 3.7 times. This darter is not colorful but has a mid-side marked with a series of twelve to fifteen dark blotches. Gill membranes are moderately to broadly joined across the throat. Branchiostegal rays usually total six. The nape, opercle, and cheek areas are fully scaled. The lateral line is complete, with seventy-two to eighty-five pored scales. Dorsal spines number eleven to fourteen, with twelve to fifteen soft dorsal rays. The first dorsal fin has an orange submarginal band.

The name “Ouachita darter” is derived from the fact that the entire distribution of this fish is within the Ouachita River system of Arkansas. It primarily occupies the upper Ouachita River above Lake Ouachita but is also found in the Little Missouri River below Lake Greeson, and in the lower Caddo River. This darter tends to live in two different habitats depending on the season. In the spring, this darter tends to prefer riffle areas with American water willow (Justicia americana) common along the edges, while in late summer, it moves to upstream areas with substrates of cobble and gravel. It does not inhabit reservoirs, and populations are destroyed when impoundment occurs.

Its diet, like that of many other darters, appears to include a variety of aquatic insects. Little is known concerning its spawning habits, but P. brucethompsoni probably spawns from March to May. A combination of small population sizes and low densities renders this darter as a species of special concern.

Although some information is available about the parasites of E. spectabile, nothing is known about the parasites of these four darters.

For additional information:
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Henry W. Robison
Sherwood, Arkansas

Chris T. McAllister
Eastern Oklahoma State College