East Fork of White River, at Bedford, Lawrence County, Indiana (Gilbert 1884).
Etymology/Derivation of Scientific Name
Macr – Greek, meaning “long”, referring to elongated forms of Hybopsis ; hyostoma – hyo = hog, and stoma = mouth (Scharpf 2005). Shoal chub, the common name, refers to the typical habitat of coarse sand and gravel raceways with strong current (Eisenhour 2004).
Macrhybopsis hyostoma recognized as distinct species in the M. aestivalis complex by Eisenhour (1999). See Eisenhour (1997) for complete synonymy.
Nocomis hyostomus Gilbert 1884:203.
Hybopsis hyostomus Jordan and Evermann (1896).
Extrarius aestivalis (Starrett 1950, 1951).
Extrarius aestivalis hyostomus (by C. L. Hubbs; see Eisenhour 2004).
Hybopsis aestivalis hyostomus Davis and Miller (1967); Becker (1983).
Hybopsis aestivalis hyostoma Cross (1967); Trautman (1981).
Hybopsis aestivalis Klutho (1983).
Macrhybopsis aestivalis hyostomus
Macrhybopsis hyostoma Eisenhour (2004); Hubbs et al. 2008:21.
Maximum size: 76 mm (3.00 in) TL (Eisenhour 1997, 2004).
Coloration: Straw color dorsally, white ventrally. Small to large pigments on dorsal and lateral regions. Pigmentation on fins variable, usually along rays of pectoral, pelvic, dorsal, anal and caudal fins. Eisenhour (2004) described life colors: translucent pale green or gray dorsally, silvery white ventrally, with broad silver lateral stripe. Concentrations of small melanophores on margins or submargins of dorsolateral scales form weakly (turbid streams) to strongly expressed (clear streams). On caudal peduncle, the lateral stripe is well to poorly defined, but fades anteriorly, centered on lateral line to one scale row above lateral line. Pectoral fin usually well-pigmented along rays; anal, pelvic, and dorsal fins with only scattered melanophores along rays or unpigmented. Eisenhour (2004) noted that specimens from the middle Red River are pallid overall, with poorly defined or absent lateral stripes and submarginal dorsolateral scale pigmentation. Of all M. hyostoma populations examined, the lateral stripe and submarginal dorsolateral scale pigmentation was most reduced in Brazos River and Colorado River populations, and Brazos River specimens were more pallid than those from the clearer Colorado River.
Counts: Pharyngeal teeth 0,4-4,0; 19 (15-21) principal caudal scales; 8 (7-10) anal fin soft rays; 7-8 (6-9) pelvic fin soft rays; 13-16 (11-18) pectoral fin soft rays; 35-38 (32-43) lateral line scales; 12-16 (2-21 predorsal scales; 5-6 (4-7) scales above lateral line; 4-5 (3-6) scales below lateral line; 12 (11-16) caudal peduncle scales; 12-16 (10-20) infraorbital pores; 10-13 (9-15) preoperculomandibular pores; 35-37 (34-39) total vertebrae; 17-18 (16-19) precaudal vertebrae; 18-20 (17-22) caudal vertebrae (Eisenhour 2004). Gill rakers on first arch usually absent, occasionally 1-2 dorsal rudiments are present (Eisenhour 2004).
Populations from the Colorado and Brazos rivers (TX) have fewer lateral-line scales and vertebrae than populations in the remainder of the M. hyostoma range. Specimens from the middle Red River have higher mean scale counts and lower mean infraorbital pore counts (Eisenhour 2004).
Body shape: Dorsally humped and ventrally flattened; rounded snout. Body fusiform with moderately thick caudal peduncle; snout moderately rounded and moderately flattened ventrally; mouth not as wide as head when viewed ventrally; lips moderately fleshy and not thickened posteriorly; eyes small and suboval to large and oval (Eisenhour 2004).
Populations in the middle Red River and the Brazos River have smaller eyes than other M. hyostoma populations; specimens from the Brazos River have smaller eyes than specimens from the Colorado River (Eisenhour 2004).
Mouth position: Horizontal and subterminal (almost inferior).
Morphology: Eyes set high on head, cross-eyed appearance when viewed from above. One or two pairs of maxillary barbels present; anterior barbels < 50% of orbit length or absent, posterior barbel length usually < orbit length; nape fully scaled or with scattered embedded scales; belly squamation variable; anal and dorsal fins bluntly pointed to slightly falcate; pelvic fins rounded to pointed; pectoral fins variable in shape and short, not reaching bases of pelvic fins in adult males; large taste buds expanded into papillae on gular area; genital papillae poorly developed as small conical or cylindrical extensions in both sexes (Eisenhour 2004). Pectoral rays 2-10 thickened in large nuptial males and bear rows of conical, antrorse uniserial tubercles; tiny tubercles rarely present on rays of dorsal and pelvic fins in large (>50 mm SL) nuptial males in peak condition (Eisenhour 2004). Populations from the Brazos River and Colorado River (TX) always lack a second pair of barbels (Eisenhour 2004); specimens from the Brazos River had longer barbels and lower average belly squamation indices than specimens from the Colorado River.
Distribution (Native and Introduced)
U.S. distribution: Widely distributed in the Mississippi River basin and the West Gulf Slope west to the Lavaca River drainage, Texas (Eisenhour 2004).
Texas distribution: Sabine River to the Lavaca River (Eisenhour 2004; Hubbs et al. 2008); Sabine, Brazos and Colorado rivers (Underwood et al. 2003).
Abundance/Conservation status (Federal, State, Non-governmental organizations)
Common in some areas whereas extirpated in many river systems throughout their range (Luttrell et al. 2002, Eisenhour 2004). Currently stable in the lower Brazos River (Runyan and Bonner, TWDB Report). Endangered status in Ohio (Scharpf 2005), Threatened status in Wisconsin (Becker 1983; Scharpf 2005). Extirpated from the Cumberland River (Etnier and Starnes 1993), the upper Kansas River drainage (Eisenhour 2004), the Arkansas River mainstem in Arkansas (Luttrell et al. 1999) and the Osage River, Missouri (Eisenhour 2004). Abundance and distribution of this species has declined in the Mississippi mainstem above the mouth of the Missouri and in the Nebraska portion of the Missouri River (Eisenhour 1997, 2004).
Macrohabitat: Medium to large rivers (Becker 1983; Eisenhour 1997, 2004; Winemiller et al. 2004). Eisenhour (1997) noted that M. hyostoma was noticeably absent in stream reaches affected by reservoirs and locks and dams or heavily modified by channelization.
Mesohabitat: Eisenhour (1997) reported collection of most individuals from deeper water (1.0-1.8 m, 3.30-6.00 ft) in strong currents over coarse sand and pea gravel; some specimens collected over fine sand or coarse gravel and cobbles; densest concentrations of individuals occurred in streams with well defined pools and riffles/runs, braided channels, and shifting sand/gravel bars. Considered a habitat specialist; both juveniles and adults preferred run habitats with clean sand or pea-size gravel substrates and moderate current velocities (20-40 cm/s; Luttrell et al. 2002). In the Mississippi River (Illinois), species was significantly associated with high water levels, a sand substrate, moderate (21-30 cm/s) current velocity, and was collected at night (65% of the time) during 24-hour sampling; species dominated the assemblage during April and May, was second most abundant in March, and was collected during every month except January (Klutho 1983); common in shallow water at night (Trautman 1981; Klutho 1983). In the Big Blue and Little Blue rivers (Kansas), species was restricted to wide, swift parts, and occurred over clean, sometimes shifting, sand bottoms (Minckley 1959). In Wisconsin, found most frequently in broad, shallow riffles over substrates of sand (62% frequency), mud (23%), clay (8%), and gravel (8%); vegetation was generally lacking and water was slightly turbid to turbid at collection sites. In the Brazos River (Texas), density of M. hyostoma was consistent through the year and rather weakly associated with peak discharge (Winemiller et al. 2004).
Spawning season: Minckley (1959) reported collection of breeding males, from the Big Blue River Basin (Kansas), in late May; and collection of males and females with well-developed gonads in mid-June at water temperature of 25°C (77°F). In Wisconsin, females with mature eggs were collected in August (Becker 1983).
Spawning habitat: Open water
Spawning behavior: Likely similar to peppered chub (Macrhybopsis tetranema), which is a flood-pulse spawner (Bottrell et al. 1964; Miller and Robison 2004):
Fecundity: Becker (1983) reported collection of a female 61 mm (2.40 in) TL weighing 1.71 g with ovaries 12.2% of the total weight containing 796 mature yellow eggs 0.7-1.0 mm (0.03-0.04 in) diameter, and white, immature eggs 0.1-0.3 mm (0.004-0.011 in) diameter; and a female 55 mm (2.17 in) TL weighing 1.38 g with ovaries 9.4% of the body weight containing 559 eggs, about half of which were mature and measured 0.65-0.8 mm (0.026-0.031 in) diameter; other females collected (thought to have recently spawned) still contained a number of mature eggs 0.8 mm (0.031 in) diameter.
Age at maturation: 1 year (Starrett 1951).
Migration: No information at this time.
Growth and Population Structure: In the Brazos River (Texas), the population consisted of at least three age groups (age 0, 1, and 2): Age-0 fish (year class 2004) were collected May – August 2004; age-1 fish (year class 2003) and age-2 fish were collected November 2003 – July 2004 (Winemiller et al. 2004). One-hundred and ninety-five age-1 individuals were collected from the Wisconsin River (Wisconsin): 109 males averaged 47.3 mm (1.86 in) TL; 86 females averaged 52.2 mm (2.06 in) TL (Becker 1983). In the Des Moines River (Iowa), age-I fish measured 18-53 mm (0.71-2.09 in) SL, in May; 24-49 mm (0.94-1.93 in) SL, in July; and 34-51 mm (1.33-2.01 in) SL, in October (Starett 1951).
Longevity: 1-2 years (Starrett 1951).
Food habits: In the Des Moines River (Iowa) fish fed on aquatic insects, small crustaceans, and plant material; Starrett (1950) classified species as a Diptera (flies and midges) feeder. Identifiable food items from the digestive tracts of 22 specimens collected from the Wisconsin River (Wisconsin) in August were: caddisflies, true bugs, dragonflies, damselflies, beatles, cycloid fish scales, and debris; 10 of the 22 digestive tracts were empty (Becker 1983) Primarily sight-feeders (Davis and Miller 1967).
Phylogeny and morphologically similar fishes
Macrhybopsis hyostoma can be distinguished from the burrhead chub (M. marconis) and the prairie chub (M. australis) by relatively large, oval eyes, posterior barbels < orbit length, anterior barbels absent or <50% of orbit length, uniserial pectoral fin tuberculation in nuptial males, absence of prominent genital papilla and head tuberculation, a moderately well-developed lateral stripe on caudal peduncle, few or no scales with clusters of small melanophores, and posterior placement of the anus (Eisenhour 2004); M. hyostoma has a moderately rounded snout, more so than in M. australis, but less than in M. marconis. Sympatric with M. marconis in the Colorado River drainage and with M. australis in the Red River drainage (Underwood et al. 2003; Eisenhour 2004).
No information at this time.
Commercial or Environmental Importance
Isolation of many M. hyostoma populations has occurred due to habitat fragmentation resulting from reservoir construction, channelization, and other anthropogenic disturbances to the hydrology of streams (Eisenhour 1997, 2004).
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Cross, F.B. 1967. Handbook of fishes of Kansas. Univ. Kansas Misc. Publ. 45:1-357.
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Eisenhour , D.J. 1999. Systematics of Macrhybobsis tetranema (Cypriniformes: Cyprinidae). Copeia 1999: 969-980.
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Winemiller, KO., F.P. Gelwick, T. Bonner, S. Zueg, and C.Williams. 2004. Response of oxbow lake biota to hydrologic exchanges with the Brazos River channel. Texas Agricultural Experiment Station and Texas State University to Texas Water Development Board. 59 pp.