Comprehensive Description
provided by Smithsonian Contributions to Zoology
Nocomis micropogon (Cope)
RIVER CHUB
Ceratichthys micropogon Cope, 1864:277 [type, ANSP 5061, Conestoga River, Pennsylvania]; 1869: 366, pl. 12: fig. 2 [redescription].—Fowler, 1909:550, pl. 27.
Hybopsis kentuckiensis.—Jordan, 1889a: 110 [part]; 1889b: 9, pl. 3: figs. 10, 11.—Goldsborough and Clark, 1908:36 [part].
NOMENCLATURE.—N. micropogon was briefly described by Cope (1864:277) from a single specimen from the Conestoga River, a tributary of the Susquehanna River, Pennsylvania, collected by a member of the Linnaean Society of Lancaster probably around 1863. Cope (1869:366), when redescribing the specimen, stated that it might be a hybrid Ceratichthys [=Nocomis] × Hypsilepis [=Notropis (Luxilus)] cornutus. Thereafter specific status of micropogon was questioned or it was synonymized with other species of Nocomis, until Hubbs (1926:27–29) used micropogon as the name for a valid species of Nocomis. Hubbs apparently based his decision on earlier descriptions of it by Cope (1864; 1869:366, pl. 12: fig. 2) and Fowler (1909:550–552) and because only one species was known to occur in the Susquehanna drainage.
Examination of the type (ANSP 5061, 67 mm SL) shows that it apparently is a hybrid Nocomis micropogon × Notropis cornutus. Cope (1869) correctly recognized that, in particular, its head resembles that of Notropis cornutus. Its anterior lateral scales are more elevated and the lateral line is more down-curved than in Nocomis and thus indicates Notropis (Luxilus) parentage. Mouth position and angle, very small size of the two barbels, and moderately large eye size are approximately intermediate between these two stocks. The breast is considerably more scaled than the Susquehanna population of N. micropogon. The holotype resembles other hybrid specimens of N. micropogon × N. cornutus, which is a common combination in our hybrid studies.
The presence of a tooth in the minor row of the type would also tend to confirm its hybrid origin. The pharyngeal teeth in N. micropogon are always 4–4, in N. cornutus 2,4–4,2. Cope (1869) reported the type to have 4–4 teeth but Fowler (1909:550) gave 1?,4–4,1?. It is not clear, but probably the arches have at least one minor tooth row; the numbers could be interpreted as 4–4 to 1,4–4,2 depending upon whether the cavities anterior to the major tooth row are regarded as tooth scars or foramina. Based upon our examination of many other Nocomis arches, at least one tooth in the minor row was present but lost when dissected by Cope. The parentage of N. cornutus is also indicated by the long and well-hooked lowermost tooth of each arch; the lowermost one in Nocomis is relatively short with a conic, lesser hook on the head.
Other characters of the type are lateral line scales about 39, caudal peduncle scales 16, anal rays 7, pectoral rays 18. Other scale counts could not be made since some scales are missing. Color pattern is not obvious since the specimen is faded.
Article 17(2) of the International Code of Zoological Nomenclature (1961:17) states that a name is or remains available even though “in the case of a species-group name, it is found that the original description relates to…an animal or animals later found to be hybrid;…” In accordance with the Code, we restrict the name Ceratichthys micropogon Cope to that presumed parent of the type specimen.
Only a few particular references pertaining to the central Appalachian area are considered in the synonymy of this wide-ranging, frequently encountered species.
DIAGNOSIS.—A species most closely related to N. platyrhynchus but differs in having fewer tubercles, reduced tubercle pattern, and larger scales. The head tubercles in adults are grouped from the snout to the interorbital area and do not extend posteriorly on the midline beyond the anterior interorbital area, forming a V-shaped pattern. Snout tubercles almost always not forming a confluent pattern with those at anterior internasal area thus causing a hiatus in tuberculation. Tubercles number fewer than 60 in almost all adults. The means for total tubercle numbers for the various river populations range from about 30 to 65. Scales larger, the mean values for circumferential scale rows and lateral line scales (Tables 8, 12) are all lower in N. micropogon than in N. platyrhynchus.
DESCRIPTION.—Morphometry: Proportional data is given in Table 25 for 51 specimens, 29 of which were grouped from the Potomac, Rappahannock, and James River drainages, with a mean length of 165 mm SL and ranging from 142 to 189 mm and 22 specimens from the Tennessee River drainage with a mean length of 161 mm and ranging from 141 to 188 mm. Although the Tennessee population shows the greatest reduction in tubercle numbers, the morphometric data agrees with that of other N. micropogon drainage populations. The head length of the Tennessee population may be somewhat shorter (mean, 27.2% of body length) than the Potomac-James group (mean, 28.4%).
The proportional features of N. micropogon are generally similar to those of N. platyrhynchus. There is some difference in the gape width between these species (Figure 5; see N. raneyi, p. 18), the heights of the regression lines are statistically different. This difference is of a subtle nature (Figure 7) and often when disassociated with body size, it was of no systematic use. A juvenile N. micropogon is shown on Figure 17.
The slope of the preopercle-opercle suture is similar to that of N. platyrhynchus; the lower portion is most often perpendicular to the horizontal body axis or it is slightly posteriorly directed (70% of 200 specimens), 24 percent with suture line very slightly directed forward, and 6 percent with suture line directed forward at an angle of about 10° to 20°.
The intestine is simple, elongate and S-shaped (39% in a sample of 75 specimens), or with a very short kink (45%) or moderate kink (16%, see Figure 8a for N. raneyi).
Meristic characters: Many of the meristic characters were segregated by drainages in order to compare populations of this wide-ranging species, and possibly to associate related populations with early dispersal and stream capture. Most of the mean values for the meristic characters in N. micropogon are lowest for its species group, but are higher than those for N. leptocephalus. The range and mean values are given for as many as 19 drainages or regions for circumferential scale rows (Table 12), lateral line scales (Table 8), scale rows above and below the lateral line (Table 11), rows of scales around the caudal peduncle (Table 14), number of pectoral fin rays (Table 16) and vertebral numbers (Table 15). The higher means for the circumferential scale rows in the Monongahela, Youghiogheny, and Potomac drainages may have been influenced by relatively recent gene interchange. The higher values in the Tennessee and Cumberland drainages contrast with the low values in nearby Kentucky, Big Sandy, and Kanawha populations. These differences also may be linked with recent drainage exchanges of N. micropogon stocks.
The breast squamation (Table 18) differs among populations from those having scaleless or only slightly scaled breasts to those completely scaled or nearly so. There is also great variation in this character within some drainages. For example, the Tennessee and Cumberland drainages contain specimens with breasts ranging from scaleless to fully scaled. The Atlantic slope drainages from the Susquehanna southward to the James consistently have few or no scales on the breast. The major drainages west of the divide, such as the Tennessee, Cumberland, Kentucky, Kanawha tributaries, Monongahela and Allegheny, show consistently higher values for the degree of breast squamation.
Tuberculation: The development, distributional pattern, and numbers of tubercles for N. micropogon is summarized in Tables 3, 4, 7, 9, 10, and 13. The relationship between increase in tubercle numbers with increase in body length for three important drainage populations of N. micropogon, and compared with N. leptocephalus, N. platyrhynchus, and N. raneyi, is shown in Figure 4. Early development and pattern of tubercle spots is illustrated in Figure 3. The distribution of head tubercles in nonbreeding males and nuptial males is shown in Figures 16, 23–25. The tuberculation in N. micropogon is characterized as having fewer tubercle numbers than N. platyrhynchus (and much fewer than N. raneyi) but appreciably more than N. leptocephalus (Figure 4). The tubercles average slightly larger than those of N. platyrhynchus but much smaller than in N. leptocephalus (Figure 24). The tubercles are distributed from the snout to the anterior interorbital area, with a hiatus almost always present between the snout and the anterior internasal area.
The tubercles first appear as light spots in the internasal area (Figure 3). They first appear in specimens 50 to 60 mm SL of both sexes, but they are sometimes not developed at sizes ranging from 60 to 75 mm SL. With increase in body length the tubercles develop on the tip of the snout and also spread posteriorly to the anterior interorbital area, where a V-pattern is formed by the absence of tubercles along the midline. The increment in tubercle numbers with increase in body length is considerably reduced at about 120 mm SL for all the river populations except the Potomac, in which reduction occurs at about 150 mm SL. The lachrymal tubercles are slowest in developing. There is usually only one or two rows of lachrymal tubercles in N. micropogon.
Tubercles are present on pectoral fin rays 2 to 4 (2 specimens); 2 to 5 (5); 2 to 6 (37), and 2 to 7 (10).
Significant aspects of the tuberculation in N. micropogon in the Potomac and Monongahela drainages are the higher numbers of tubercles and a more posterior distribution, sometimes extending to the posterior interorbital area. In tuberculation, and in some meristic characters, N. micropogon of these drainages closely approaches character values of N. platyrhynchus. Possible introgressive hybridization of these two species resulting from exchanges of stocks via the Greenbrier-Monongahela-Potomac drainages is discussed in the section on dispersal (p. 66). The Potomac and Monongahela populations are very similar in respect to total number of tubercles, increase in numbers with increase in body length and the relative variation of tubercle numbers by size groups (Table 7). The James drainage population (Table 10), which is to the south of the Potomac, and the Susquehanna population, which is to the north (Table 13), have similar numbers of tubercles and appreciably fewer than the Potomac population. N. micropogon from the Tennessee drainage has the lowest number of tubercles (Table 9) for the species. The average values for tubercle numbers of mature males of varying body lengths were: Potomac-Monongahela population, about 50 to 65; James, Susquehanna, and west of Allegheny Mountains, about 40 to 50; Tennessee drainage, about 30.
Nuptial crest: Nuptial crests or swellings were observed on specimens of various sizes. Some swelling and moderate to large crests were found on specimens in the following standard length size-groups: 100–119, 2 specimens; 120–139, 2 (4 with crests); 140–159, 5 (19); 160–179, 6 (10); 180–199, 3 (5); 200–219, 1 (1). These data, as with that pertaining to the development of tubercle buds (Table 4) and the presence of tubercles or scars (Table 3), suggest that different males mature at different sizes or ages, or that they mature and spawn more than once. Since tubercle scars are present on nonbreeding males that are developing tubercle buds, it is assumed that some males spawn more than one season.
Pharyngeal dentition: The tooth count is 4–4 (Figure 18) in 34 pairs of arches in which the specimens were sampled over the range of the species. The teeth and arch are like that of N. platyrhynchus.
Coloration: Only particular aspects of the coloration of N. micropogon will be discussed because much of the salient color and pattern has been treated above under the two other group members. Lachner (1952:437–439) described the coloration of N. micropogon, chiefly from specimens from the northeastern portion of its range, the Allegheny, upper and middle Susquehanna and Lake Ontario drainages. It was noted that a dark horizontal midlateral stripe is prominent in the young and juveniles of N. micropogon while only faintly visible in formalin preserved specimens of adult males. In the large number of preserved adults now available, we find that a majority of specimens have a dark lateral stripe, but it may be faded or absent in preservation. The lateral stripe is present in specimens over the geographic range of the species. Its relative frequency of occurrence, portions of the body on which it is developed and the intensity in adult males and females agree with that of N. platyrhynchus.
Reighard (1943:400) observed that living young males of N. micropogon with tuberculate heads have a well-marked lateral stripe. He did not state this for the large nuptial males engaged in reproductive activities. Lachner (1952:438) stated that nuptial male N. micropogon do not show a conspicuous dark lateral stripe in life as was observed in N. biguttatus. Our recent observations on nest-building males from the upper Susquehanna drainage show that a light stripe is effected by light green medians of the scales, or a moderate to heavy dark stripe by the blackish scale margins on the midlateral level; the intensity of the stripe can change rapidly. The light green medians of the scales were also seen in living juvenile and adult males and females from the James, Potomac, and upper Tennessee drainages. Upon preservation, the medians of the scales turn light to dark slate color. The lateral stripe was similar to that of living N. platyrhynchus.
The pink-rosy nuptial coloration of the male is developed in the same area of the body as in N. raneyi and N. platyrhynchus. It has been observed in males from Lake Ontario, upper and middle Susquehanna, Rappahannock, James, upper Tennessee, and Allegheny drainages. Reighard (1943:400) reported it from Michigan. The most intensely colored male we have seen, 160 mm SL (CU 48579), was captured in the upper Susquehanna on 30 May 1965 during the spawning period. Its rosy color was developed dorsad to three scale-rows above the lateral line. The medians of the scales in the lateral stripe area were very light pink, lighter than those above and below, with the light green color barely present.
The olive-yellow middorsal stripe described for juveniles of both sexes and smaller adult females of N. raneyi is generally present in the same life stages and sexes of N. micropogon as well as in N. platyrhynchtis. It was also present, but faint, on the largely blackish dorsum of a captured living nuptial male N. micropogon of 150 mm SL.
The coloration of the paired and anal fins of N. micropogon is similar to that of both N. raneyi and N. platyrhynchus. The yellow pelvic fin coloration of a nuptial male after one week in preservative approached that of the specimens of N. platyrhynchus (USNM 194870). Lachner (1952:438) noted white coloration on the tips of the rays of the paired and anal fins of nuptial males and we have observed it on the tips of the anterior dorsal fin rays of a nuptial male.
Caudal and dorsal fin coloration may show some geographic differentiation. There appear to be two types of caudal color pattern, an orange-reddish one in populations from the southern part of the range, and an olive, olive-orange, or olive-yellow one in northern populations. The distinctiveness of these color differences is not clear and little data are available on variation in shades. The caudal fin in juveniles to adults of the southern populations is fairly reddish in color, approaching that of N. raneyi, and much like that of N. platyrhynchus. The distal caudal and dorsal membranes were light orange-red, the basal membranes being olive in several postnuptial males and females and nonbreeding adult males collected in the upper James drainage during late July 1963. A highly tuberculate crested male with nuptial color from the Rappahannock drainage had an orange-reddish outer caudal. The most striking caudal coloration yet seen in N. micropogon was that of five postnuptial males (USNM 194689) having tubercles or tubercle scars, crests, and pink lower coloration, taken in the upper North Fork of Holston River, Tennessee drainage on 2 July 1963. The caudal fin color, a bright orange-red, was developed over most of the fin which was largely olive basally.
The orange-red caudal fin (color over half of entire fin and, in some, over anterior distal dorsal fin) has been observed by us in living or freshly preserved specimens of the following growth stages: lower Potomac, living juveniles; Shenandoah of Potomac, preserved adult males; upper Rappahannock, preserved juveniles and an adult male; upper James, living juveniles and adults; Powell, Clinch, and North Fork Holston of upper Tennessee, living juveniles and adults. Carter R. Gilbert (personal communication) has observed N. micropogon with reddish caudals in the upper Cumberland drainage. The “olive” caudal fin appears to be characteristic of northern populations. In Catatonk Creek, upper Susquehanna drainage, juvenile and adult females and nonbreeding males generally have yellow-olive rays, sometimes appearing amber. Distally the membranes are translucent grayish olive; basally they are more grayish, tending to be clear. All specimens from Catatonk, except one nuptial male captured in May 1965 lacked reddish or orangish coloration. The exception, a highly rosy-colored male N. micropogon had a faint yellow-orange in the distal one half to two thirds of the membranes of the caudal lobes and a tinge of this color in the distal portion of the medial membranes. Lachner (1952:438) stated that the dorsal and caudal fins of N. micropogon were yellowish with some red near the tips of the rays; his specimens were from Lake Ontario tributaries, upper and middle Susquehanna, and the Allegheny drainages. Hubbs and Lagler (1958:69) state that the caudal fin of N. micropogon is not red, in contrast to the red caudal fin of young N. biguttatus in life. Trautman (1957:86, 295) stated that N. micropogon in Ohio (Great Lakes and Ohio River basins) has a slate-colored caudal that is never flushed with red, that it may be a faint orange in some young and that it may have a reddish or orange tinge in specimens only from polluted waters. Information is lacking on details of caudal fin coloration in the Ohio basin of Indiana and much of Kentucky and West Virginia. Most of the freshly preserved juveniles and a ripe female in two series from Deer Creek, Susquehanna River, near its mouth, taken during the 1965 spawning season, had faint tinges of reddish orange on the distal membranes of the caudal.
In summary, there appears to be some evidence that two caudal fin color forms exist. The difficulty in evaluating the significance of these color forms is that we lack comparative data. We have observed the two forms from different geographical areas, but we know little of the exact areas or drainages each occupies, and of the intermediate areas or regions in which both forms may occur. We know that some colors can be intensely developed, or “turned on,” in Nocomis within a few seconds, but this was not noted for caudal color. We have resorted to color guides only in the laboratory; none were used in the field other than, occasionally, colored objects, such as differently colored plastic chips. The shades of red, reddish orange or olive-orange, and the reflections from these colors, in free-living and freshly captured specimens may be variously interpreted by different individuals at different times. Specimens were seen, or available for observation, one at a time, spread out over years of observations by any one individual, and thus comparative, objective data were not obtained.
POPULATIONS.—The northern drainage populations of the river chub, from Michigan to New York, are very much alike. The principle area of differentiation, excluding the caudal fin color forms discussed above, is in the drainages of the central Appalachian region. Here the interesting divergence is in the Potomac and upper Monongahela drainage populations, both having finer scales, higher tubercle numbers, and more extensive distribution of tubercles than in river chubs of adjacent drainages. The Tennessee drainage population has a notable reduction in numbers of head tubercles, as well as having shorter heads. The most southern population of the Atlantic slope, in the James drainage, resembles the northern populations in respect to tubercle numbers and distribution. Populations in the Kentucky drainage and in tributaries of the Kanawha drainage are fine-scaled compared to Cumberland and Tennessee drainage stocks. N. micropogon of the Atlantic slope streams typically have reduced squamation on the breast or have the naked condition.
We find no significant differentiation over the range of the river chub to merit recognition of subspecific populations. The similarities in some of the drainage populations may be related to stream capture and early dispersal of stocks.
REPRODUCTION AND GROWTH.—The nest-building, reproduction, age and growth of N. micropogon is discussed by Lachner (1952) and compared with N. biguttatus and N. leptocephalus. Of the thousands of specimens recently examined, one specimen of N. micropogon (Table 7) from the Potomac drainage just exceeded 200 mm SL and another, by far the largest specimen known, measured about 270 mm SL. This large crested nuptial male (TU 8928) is recorded from Lake Pontchartrain, Mandeville, Louisiana, May 1877, “collection of G. Kohn, New Orleans, La.” A few tubercles are intact and these plus the tubercle scars total 60, a typical number for the species. The tubercle pattern is also normal for the species. The locality is completely out of the known range for N. micropogon. The specimen consists of the head and entire skin of the body attached to the head, including the fins. It probably was an item of curiosity and could have been hand-transported down the Mississippi by the river traffic of the time.
MATERIALS EXAMINED.—Data were taken from 395 collections. The total number of collections studied from each of 18 drainages is given and these are further subdivided by the institution and number of collections housed.
Susquehanna 24: CU 8, UMMZ 2, USNM 14. Chesapeake Bay tribs. 10: CU 3, UMMZ 7. Potomac 30: CU 8, UMMZ 2, USNM 20. Rappahannock 19: CU 8, UMMZ 3, UR 1, USNM 7. York 3: UR 1, USNM 2. James 54: ANSP 1, CU 11, UMMZ 7, USNM 34. Savannah 4: CU 1, TU 2, USNM 1. Tennessee 77: CU 3, DU 1, UMMZ 39, USNM 34. Cumberland 27: CNHM 1, CU 5, Ind. U. 1, SU 1, TU 2, UMMZ 13, USNM 4. Kentucky 21: CNHM 1, KFW 2, UMMZ 5, USNM 13. Big Sandy 8: CU 1, UMMZ 1, USNM 6. Guyandot 5: CU 1, UMMZ 1, USNM 3. Coal, Kanawha 10: CU 1, UMMZ 1, USNM 8. Elk, Kanawha 10: CU 5, UMMZ 5. Ohio tribs., W. Va. 5: CU 3, USNM 2. Monongahela 52: CU 6, USNM 46. Allegheny 20: CU 1, UMMZ 4, USNM 15. Lake Erie-Ontario, N. Y. 23: CU 7, USNM 16.
DISTRIBUTION.—N. micropogon is native to a large portion of northeastern United States and does not occur west of the Mississippi River. Its range on the Atlantic slope is southward from the Susquehanna drainage in New York to the James drainage in Virginia, absent southward except for a population in the upper Savannah drainage. The only known population on the Gulf of Mexico slope occurs in one river system of the upper Mobile Bay drainage. West of the Appalachian divide it occurs from the Tennessee drainage tributaries of northern Alabama and southwestern Tennessee, and from die Wabash drainage of Illinois (P. W. Smith, 1965:7), up (eastward) throughout most of the Ohio River basin. It is found in the Great Lakes drainage of the Lower Peninsula of Michigan eastward to Lake Ontario tributaries in New York and Ontario. The river chub is apparently absent from significant portions of some drainages, and the entire length of other drainages, mainly within the southwestern lowland portion of this general range.
N. micropogon occurs in all major drainages tributary to the western shore of Chesapeake Bay, from the Susquehanna to the James (Figure 19). Records are available from throughout most of the Susquehanna drainage of New York and Pennsylvania (except from some large, poorly collected, and polluted areas), to near its mouth in Maryland. It occurs in all minor Chesapeake Bay drainages of sufficient size from Swan Creek to Patuxent River, Maryland. Most Potomac drainage records are from throughout the upper and lower main basin in Maryland and Virginia including its large tributary, the Shenandoah River system of Virginia. This species may be rare in the North and South Forks and North and South Branches of the Potomac River, largely in West Virginia and western Maryland. Relatively few specimens were seen from this montane region, but it has been poorly collected. The river chub occurs in all major upper Rappahannock drainage tributaries, Virginia, and has been taken from its lower freshwater portion just above the Fall Zone. Six locality records of N. micropogon from the York drainage, Virginia, indicate that it is widespread therein.
N. micropogon occurs throughout most of the James drainage of Virginia and West Virginia. The river chub was taken in 68 collections from 63 localities of the 182 James drainage collections that include Nocomis. The majority of the collections are from major upper tributaries, such as the Jackson River, Back, Dunlap, and Potts Creeks and, in the middle portion, the James, Maury (North) River and its tributaries. Three collections are from the Piedmont-based Appomattox River, the longest James tributary; two are from its headwaters, the other in Swift Creek, a tributary entering the Appomattox near its mouth in the James River estuary.
The river chub occurs commonly above and below the restricted range of N. raneyi in the James but is rare within the range of N. raneyi (Figure 20). Only 13 or 14 specimens of the river chub were captured in the Craig Creek system compared to 742 specimens of N. raneyi. Six specimens of N. micropogon (TU 25469) were taken with one specimen of N. leptocephalus and three hybrid N. leptocephalus × N. micropogon from upper Johns Creek, near Maggie. N. micropogon and N. raneyi are known to have been collected together only three times, all from the lower half of Johns Creek. The upstream and downstream localities are believed to be accurate but the location of the middle station is approximate. Specimens UMMZ 135401 and 181830 were from the latter station, which was reported by G. W. Burton to be “seven miles above Newcastle.” It was plotted by measuring seven miles above (upstream from) Newcastle along State Route 311 and County Route 658. Two specimens of N. micropogon (UMMZ 135413) are from Craig Creek, and were collected by Burton, supposedly 25 miles west of Newcastle. No point on Craig Creek is 25 air- or roadmiles west of Newcastle. The collection is located as 25 roadmiles on Route 311 and County Route 621 southwest (upstream from) Newcastle. This probably is still erroneous since the locality would be in the extreme headwaters. Craig Creek, from this locality to four miles downstream, is quite small, about 4–10 feet in width, smaller than streams typically inhabited by the river chub. Presumably, the specimens are from Craig Creek, although probably from somewhat below the given locality. From correspondence of Burton it is indicated that he collected only in the Craig system, James drainage. Our numerous attempts to find a river chub in the Craig system were unsuccessful although one juvenile specimen (CU 47584), tentatively identified as this species, was collected at the mouth of Craig Creek.
Only one specimen of N. micropogon (CU 50610) from Catawba Creek was found, this being from the headwaters. Hybrid N. leptocephalus × N. micropogon (USNM 171685) and N. micropogon × N. raneyi are known from the middle Catawba. N. leptocephalus is common throughout Catawba Creek.
N. micropogon apparently is common in sizable streams surrounding the Craig and Catawba Creek areas. Upriver, nearest to the range of N. raneyi, the river chub (USNM 132064) was collected from Mill Creek in 1885, near its mouth in the James River at Gala, approximately five rivermiles upstream from the mouth of Craig Creek, and in other streams shown in Figure 19. It is widely distributed in the Maury River whose mouth is 16 rivermiles above that of the Pedlar River system, from which a specimen of N. raneyi was taken.
The five specimens upon which Fowler (1945:77) based his record of N. micropogon from the Roanoke drainage were found to be N. leptocephalus.
The ten records (CU, TU, USNM) of N. micropogon from the Chatooga and Keowee River systems, upper Savannah drainage, South Carolina and Georgia, indicate widespread occurrence therein. Another locality is in the Savannah River, Abbeville County, South Carolina. Most of these localities were plotted by Lachner and Jenkins (1967: fig. 7). N. leptocephalus was taken in only one of the eleven collections.
Our only records of N. micropogon on the Gulf slope (TU, 5 collections) are from the Coosawattee system (upper Coosa) of the Mobile Bay drainage in Gilmer County, northwestern Georgia. These collections were noted by Suttkus and Ramsey (1967:139–140).
Within the New-Kanawha system, N. micropogon is known only below Kanawha Falls, from Coal and Elk Rivers, the two largest tributaries of the Kanawha drainage. Specimens were taken from upper and lower Coal River; those from Elk River are all from the upper portion. No specimens of chubs were available from other Kanawha tributaries. The fauna here and elsewhere in West Virginia has been largely extirpated by mining (Goldsborough and Clark, 1908:31–32; Kinney, 1964:22–24) and industrial pollution.
The wide occurrence of N. micropogon in the southwestern Ohio River basin was discussed and illustrated by Lachner and Jenkins (1967). Its distribution north of the Ohio River, in Indiana and Ohio, was analyzed and mapped respectively by Gerking (1945:48–49, map 25) and Trautman (1957:296, map 61). The river chub is also widely distributed in most of the remainder of the Ohio basin of West Virginia, Pennsylvania, and New York.
Within the Great Lakes drainage, N. micropogon occupies streams of the entire lower Peninsula of Michigan (Hubbs and Lagler, 1958:78), thence eastward, within Ontario Province streams of the Lake Huron basin south of Georgian Bay and the northern Lake Erie basin, to approximately the midlength of the northern Lake Ontario basin (Radforth, 1944:59–60, fig. 22). It ranges eastward, from the southeastern corner of Michigan, in streams of southern Lake Erie, including the Maumee River drainage of Ohio (Trautman, 1957:296–297, map 61), and Lake Ontario basins to the Finger Lakes drainage of New York. However, within the southern Lake Ontario basin, this species is apparently absent from the entire Genesee River drainage, since it was not reported by Greeley (1927) and later collectors. It is common in Salmon Creek which enters Lake Ontario six miles west of the Genesee mouth. East of the Salmon Creek mouth there is a 52 mile gap in its distribution, ending at Blind Sodus Creek, whose mouth is 16 miles west of the mouth of Oswego River, the Finger Lakes outlet. Within the Finger Lakes drainage, N. micropogon is known from Catherine Creek, which enters the south end of Seneca Lake, the Cayuga Lake basin and one record is from a Seneca River tributary downstream from Cayuga Lake.
The leptocephalus Group
DESCRIPTION.—Nuptial males develop few tubercles (Figure 4) on head, numbering fewer than 30 and often less than 20 (Table 19). In populations of the south Atlantic and Gulf slope drainages the nuptial males have even fewer tubercles, in some, averaging about 6. Tubercles extend from internasal area to occiput, depending on subspecies. Tubercles absent on snout and lachrymal areas. A large, nuptial crest developed by larger males positioned more anteriorly than in the micropogon group. Breeding coloration of nuptial male bluish on head and body or, body with orange, brassy or tan lateral stripe. Dark marking on anterior portion of scale in adults narrower than micropogon group. Caudal spot dark, small, indistinct in juveniles (compared to large, distinct spot in biguttatus group). Intestine almost always with a ventral whorl (except in some collections from southeastern United States). Dentition 4–4 to 3–3. Scales large, body circumferential scales range from 26 to 33. Body comparatively short and stocky; snout blunt; posterior edge of preopercle usually vertical or sloped posteriorly below. Males attain an intermediate size for genus except one southeastern population which is larger. Males of the three subspecies construct .small to moderately sized moundnests of fine to small gravel. The three subspecies include Nocomis l. leptocephalus of the Atlantic slope from the Potomac and New drainages southward to the Savannah River; a new subspecies (see paper 2, p. 2) of the southeast Appalachian slope in the Savannah, Altamaha and Apalachicola drainages; and Nocomis l. bellicus of the southern Gulf slope in the Mobile drainage westward to certain eastern tributaries of the Mississippi River.
- bibliographic citation
- Lachner, Ernest A. and Jenkins, Robert E. 1971. "Systematics, distribution, and evolution of the chub genus Nocomis Girard (Pisces, Cyprinidae) of eastern United States, with descriptions of new species." Smithsonian Contributions to Zoology. 1-97. https://doi.org/10.5479/si.00810282.85
