Geographic Variation in the North American Cyprinid Fish, Hybopsis gracilis Part 1

Geographic Variation in the North American Cyprinid Fish, Hybopsis gracilis.

by Leonard J. Olund and Frank B. Cross.

INTRODUCTION

The flathead chub, _Hybopsis gracilis_ (Richardson), occurs in the Plains Region of Canada and the United States, in four major drainage systems: Mackenzie River, which discharges into the Arctic Ocean; Saskatchewan River, which discharges into Hudson Bay via Nelson River; and Missouri-Mississippi System and Rio Grande, both draining into the Gulf of Mexico. Each of these systems is occupied in part only. In the Mackenzie Basin, _H. gracilis_ has been reported as far north as Fort Good Hope (Walters, 1955:347). Flathead chubs occur in the Saskatchewan Basin from Alberta eastward to Lake Winnipeg, Manitoba, but have not been found in other streams that flow into Lake Winnipeg (Red River, Brokenhead River and Whitemouth River) nor in Nelson River downstream from Lake Winnipeg. In the Missouri Basin the species occurs more or less continuously from the high plains adjacent to the Rocky Mountains in Montana and Wyoming down the mainstream of the Missouri River to its mouth, and down the mainstream of the Mississippi River as far as Barfield, Arkansas, but not to the Gulf. The species probably attains its greatest abundance in the Missouri Basin, but it is scarce or absent in tributaries north and east of the Missouri mainstream, in the South Platte Basin, and in the central part of the Platte River in Nebraska.

The flathead chub is unknown in the Mississippi Basin above the mouth of the Missouri River, and in the Ohio River Basin above its mouth. In the Arkansas River Basin, records are restricted to (1) the headwaters and tributaries of the Arkansas River from eastern Colorado downstream as far as Garden City, Kansas, (2) the Cimarron River at Kenton, Cimarron County, Oklahoma, and (3) the South Canadian River and tributaries from northeastern New Mexico eastward as far as Norman, McClain County, Oklahoma, but rarely there. Thus, the range in the Arkansas Basin seems to consist of three isolated segments. Likewise, isolated populations exist in the Rio Grande System, where flathead chubs are confined to the upper parts of the Rio Grande and Pecos basins, above the confluence of the Rio Grande and Pecos Rivers. Records resulting from introductions have been reported for the Gila River by Koster (1957:62) and from the Snake River, Wyoming, by Simon (1946:72).

Six names apply to the flathead chub, the earliest of which is _Cyprinus gracilis_ Richardson (1836:120). Other names have sometimes been accepted as applicable to valid species and/or subspecies, but usage, diagnoses, and stated ranges have been confusingly inconsistent. For most of the past 100 years, _Platygobio_ Gill has been recognized as the appropriate generic name for the flathead chub, but Bailey (1951:192) places _Platygobio_ and other nominal genera of barbeled minnows having short guts, protractile premaxillae, and four teeth (primary row) in the single genus _Hybopsis_ (Aga.s.siz, 1854). Strangely, the orthotype of _Hybopsis_, _H. gracilis_ Aga.s.siz, is a junior synonym of _H. amblops_ (Rafinesque) (Hubbs and Ortenburger, 1929b:66) and is a younger name than _C. gracilis_ Richardson.

The purpose of this paper is to redescribe the species and to make known its pattern of geographic variation. Natural history will also be considered, as will habitat, food habits, and breeding season.

METHODS, MATERIALS AND ACKNOWLEDGMENTS

Ten meristic characters and seventeen measurements of body-parts (the latter expressed as proportions of standard length) have been a.n.a.lyzed.

They are: number of rays in the dorsal, a.n.a.l, caudal, pectoral and pelvic fins; number of scales in the lateral line, before the dorsal fin, around the body and around the caudal peduncle; number of vertebrae; body-depth, depth of caudal peduncle, length of caudal peduncle, predorsal length, length of depressed a.n.a.l and dorsal fins, length of pectoral and pelvic fins, head-length, head-depth, head-width, snout-length, pos...o...b..tal length of head, length of orbit, interorbital width, length of upper jaw and width of gape.

Counts and measurements were made as described by Hubbs and Lagler (1958), with the exception of scales before the dorsal fin, which were counted as the number of vertical scale-rows between the upper margin of the opercular cleft and the origin of the dorsal fin. Vertebral counts, made from roentgenograms, excluded vertebrae in the Weberian complex (presumably always four) but included the hypural vertebra.

Counts and measurements were made on series (usually ten fish) from localities throughout the range. To minimize effects of allometric growth, the fish were divided into several length-groups prior to a.n.a.lysis of proportional measurements: 30-50mm, 50-70mm, 70-100mm, 100-150mm, 150-200mm and 200mm standard length and over. The majority of specimens examined were 70-100mm in standard length.

Specimens were obtained from the following inst.i.tutions: University of Alberta (abbreviated UA in the text); Museum of Zoology, University of Michigan (UMMZ); University of Missouri (UM); Montana State College (MSC); University of Oklahoma Museum of Zoology (UOMZ); University of Saskatchewan; Royal Ontario Museum, Division of Zoology, Toronto (ROMZ); University of Wyoming (WU); Museum of Natural History, University of Kansas (KU). Specimens examined are listed in the accounts of the subspecies.

We are grateful to D. A. Boag, Reeve M. Bailey, Arthur L. Witt, C. J. D.

Brown, Carl Riggs, F. M. Atton, W. B. Scott, and George Baxter, all staff-members of the inst.i.tutions listed in the immediately preceding paragraph, for placing specimens at our disposal. Mr. William Peters a.n.a.lyzed the contents of stomachs of specimens that were used for study of the food habits. Mr. Artie L. Metcalf a.s.sisted in collecting specimens. Drs. Kenneth B. Armitage and E. Raymond Hall offered valued suggestions in connection with the preparation of the ma.n.u.script.

DESCRIPTION OF THE SPECIES

=Hybopsis gracilis= (Richardson)

Flathead Chub

(Synonymy under accounts of subspecies)

_Description._--Pharyngeal teeth 2,4-4,2, hooked; dorsal fin of moderate size, falcate, first princ.i.p.al ray longest, extending beyond posterior rays in depressed fin, its origin usually slightly in front of insertion of pelvic fin, approximately equidistant from tip of snout and base of caudal fin, rays 8, rarely 9; pectoral fin strongly falcate, rays 14-20, usually 16-18; pelvic rays 8, rarely 9; a.n.a.l fin falcate, rays 8, rarely 9; caudal rays 19, rarely 20.

Body slightly compressed, nearly terete; head-length 23.1-28.8 per cent of standard length; head broad and flattened, snout subconical, premaxillae protractile, upper lip not medially expanded; mouth subterminal, nearly horizontal, large; a single pair of terminal maxillary barbels; orbit usually 5-7 per cent of standard length; lateral line slightly decurved; intestine short, peritoneum silvery.

Color brown or olivaceous dorsally, silver or creamy white ventrally, without distinctive markings; dusky lateral band evident in preserved specimens.

Taste-buds present on membrane between first and second princ.i.p.al rays of all fins, and on first to sixth interradial membranes of pectoral fin. On the caudal fin, taste buds between first and second princ.i.p.al rays of upper and lower lobes, though present, are less well developed than on other fins. Moore (1950:88) states that taste buds are numerous on the barbels, cheeks, lips, chin, snout, opercles and branchial membranes, and are present in decreasing numbers over the body.

Nuptial tubercles of male minute and densely scattered over top of head and snout; usually present on pectoral rays 1-8, weak when present on rays beyond the eighth, never found beyond the eleventh ray; minute tubercles usually found on dorsal, pelvic and a.n.a.l fins, rarely on lower scales of caudal peduncle; predorsal scales have a fine peripheral row of tubercles.

=Hybopsis gracilis gracilis= (Richardson)

(Plate 22)

_Cyprinus (Leuciscus) gracilis_ Richardson, 1836:120 and Pl. 78 (original description; Saskatchewan R. at Carlton House).

_Coregonus angusticeps_ Cuvier and Valenciennes, 1848:534 (original description; Saskatchewan R.).

_Pogonichthys communis_ Girard, 1856:188 (in part; original description); Girard, 1858:247 and plate 55 (in part; characters; synonymy); Suckley, 1860:361 (Milk R.); Cope, 1879:440 (Fort Benton, Mo. R.; Judith R.).

_Platygobio gracilis_, Jordan and Gilbert, 1882:219 (in part; characters; synonymy); Graham, 1885:74 (Kansas R.; synonymy); Jordan, 1885:29 (records); Jordan and Meek, 1886:13 (Mo. R., St.

Joseph, Mo.); Meek, 1892:245 (characters; Mo. R., Sioux City, Iowa); Eigenmann, 1895:111 (Craig; Poplar; Brandon; Medicine Hat); Meek, 1895:137 (Platte R., Fremont, Neb.); Evermann and c.o.x, 1896:412 (in part; habitat; synonymy); Jordan and Evermann, 1896:326 (in part; characters; synonymy); Thompson, 1898:214 (Brandon; Saskatchewan R.); Evermann and Goldsborough, 1907:98 (records from Canada); Forbes and Richardson, 1920:170 (characters; habitat; synonymy; records from Illinois; but Fig.

45 is _Hybopsis meeki_ Jordan and Evermann, not _H. gracilis_); Hankinson, 1929:446 (records from North Dakota); Jordan, 1929:76 (in part; characters); Jordan, Evermann and Clark, 1930:136 (in part; synonymy); Churchill and Over, 1933:45 (characters; food; habitat; sp.a.w.ning; records from South Dakota); O'Donnel, 1935:481 (Ohio R., Cairo, Ill.; Miss. R., Chester, Ill.); Hinks, 1943:57 (records from Canada); Clemens, _et al._, 1947:17 (records from Saskatchewan); Dymond, 1947:19 (distribution in Canada); Rawson, 1951:208 (Great Slave Lake; Mackenzie R.); Shoemaker, Pickering and Durham, 1951:84 (Miss. R., Cates, Tenn.; Miss. R., between Hickman and Barfield, Ark.); Wynne-Edwards, 1952:18 (distribution in Canada); Miller and Paetz, 1953:47 (Peace R. at town of Peace River); Walters, 1955:347 (distribution in Canada; dispersal into Canada); Keleher, 1956:265 (Saskatchewan R., Manitoba); Lindsey, 1956:771 (distribution in Canada); Keleher and Kooyman, 1957:110 (Kelsey Lake, Manitoba); Lindsey, 1957:657 (Laird and Peace drainages, British Columbia); Scott, 1958:16 (distribution in Canada); Slastenenko, 1958:7 (distribution in Canada).

_Platygobio pallidus_ Jordan and Gilbert, 1882:220 (original description; Ohio R., Cairo, Ill.); Jordan and Evermann, 1896:326 (characters; synonymy; Ohio R., Cairo, Ill.); Jordan, Evermann and Clark, 1930:136 (Ohio R., Cairo, Ill.; synonymy).

_Platygobio gracilis communis_, Simon, 1946:71 (in part; characters; food; habitat; sp.a.w.ning); Moore, 1950:87 (habitat; sense organs).

_Hybopsis gracilis communis_, Bailey, 1951:192 (record from Iowa; key); Harlan and Speaker, 1951:75 (characters; distribution in Iowa); Hubbs, 1951:9 (habitat; Miss. R.); Harrison and Speaker, 1954:516 (habitat); Personius and Eddy, 1955:42 (habitat; Little Mo. R.).

_Hybopsis gracilis_, Cleary, 1956:271 (record from Iowa; distributional map); Bailey, 1956:332 (record from Iowa; key); Harlan and Speaker, 1956:90 (characters; distribution in Iowa); Eddy, 1957:111 (in part; characters; key); Moore, 1957:110 (in part; key); Underhill, 1959:100 (Vermillion R., South Dakota).

_Diagnosis._--Post-Weberian vertebrae 40-42, usually 41-42; lateral line scales 50-56; pectoral rays 15-20, usually 17 or more; head-depth 12.3-15.1 per cent of standard length, usually 14.7 per cent or less.

See Figs. 1 and 2.

_Other characters._--Circ.u.mference scale-rows 31-42; predorsal scale-rows 20-29; size large, as much as 246 mm standard length (see Fig. 1 of Pl. 24); head-length 23.4-27.4 per cent of standard length, usually 25.5 per cent or less; pos...o...b..tal length of head 10.9-13.9 per cent of standard length, usually 12.5 per cent or less; predorsal length 46.0-51.7 per cent of standard length; orbit 5.1-6.8 per cent of standard length; prepelvic length 46.6-52.2 per cent of standard length; caudal peduncle length 17.2-22.1 per cent of standard length.

_Range_ (Plate 21).--Mackenzie Basin south from Fort Good Hope; Saskatchewan Basin east to Lake Winnipeg; mainstream of Missouri River and Mississippi River south to Barfield, Arkansas; intergrading with _H.

g. gulonella_ in upper Missouri Basin and lower parts of major tributaries to Missouri River in Nebraska and Kansas.

_Specimens examined._--Below are listed museum numbers, number of specimens (in parentheses), localities, and year of collection.

Collections marked with asterisk (*) are intergrades more closely resembling _H. g. gracilis_ than _H. g. gulonella_. Records from literature are cited in the synonymy.

ALBERTA: UA (6), Milk R. at town of Milk River, 1950; UA (3), Athabasca R. at Fort McMurray, 1955; UA (1), Red Deer R. at Steveville, 1952; UA (2), Peace R. at town of Peace River, 1952; UA (11), Peace R. at Dunvegan, 1956; UA (2), Simonette R. tributary to Smoky R., date unknown; ROMZ 17704 (1), Milk R. W town of Milk River, 1955.

ARKANSAS: UMMZ 128573 (5), Mississippi Co., Mississippi R., 1939.

ILLINOIS: UMMZ 134799 (146), Mississippi R. at Grand Tower, 1936; UMMZ 147045 (8), Mississippi R. at Cairo, 1944.

KANSAS: KU 1234 (173), Leavenworth Co., backwater of Missouri R. near Corral Cr., 1940; * KU 1814 (1), Douglas Co., floodpool of Kansas R., below Lakeview, 1951; * KU 1825 (1), Douglas Co., floodpool of Kansas R., 1951; * KU 1841 (56), Douglas Co., Kansas R. at Lawrence, 1951; * KU 1898 (6), Douglas Co., floodpool of Kansas R., 1951; * KU 1911 (5), Douglas Co., floodpool of Kansas R., 1951; * KU 1928 (2), Jefferson Co., floodpool of Kansas R., 1951; KU 3850 (30), Atchison Co., Missouri R., 1957; * KU 4377 (2), Douglas Co., Kansas R. at Lawrence, 1958; * KU 4655 (2), Douglas Co., Kansas R. at Lawrence, 1959.

MANITOBA: ROMZ 13834 (1), Kelsey Lake, 25 miles east of the Pas, no date; ROMZ 14500 (25), Saskatchewan R. at the Pas, 1947; ROMZ 16325 (1), Lake Winnipeg, no date.