March
Notes
1995
HAFNER,J. C., AND M. S. HAFNER. 1983. Evolutionary relationships of heteromyid rodents. Great
Basin Nat. Mem., 7:3-29.
HENNIG,W. 1965. Phylogenetic systematics. Ann.
Rev. Entomol., 10:97-116.
HOMAN,J. A., AND H. H. GENOWAYS.1978. An
analysis of hair structure among heteromyid rodents. J. Mamm., 59:740-760.
RYAN,J. M. 1989. Comparative myology and phylogenetic systematics of the Heteromyidae (Mammalia, Rodentia). Misc. Publ. Mus. Zool., Univ.
Michigan, 176:1-103.
STANGL,F. B., JR., AND E. M. JONES. 1987. An
assessment of geographic and seasonal biases in systematic mammal collections from two Texas universities. Texas J. Sci., 39:129-137.
107
WILLIAMS,
D. F. 1978. Karyological affinities of the
species groups of silky pocket mice (Rodentia, Heteromyidae). J. Mamm., 59:599-612.
WILLIAMS, D. F., H. H. GENOWAYS,AND J. K. BRAUN.
1993. Taxonomy. Pp. 38-196, in Biology of the
Heteromyidae (H. H. Genoways and J. H. Brown,
eds). Amer. Soc. Mamm., Spec. Publ., 10:1-719.
WOOD, A. E. 1935. Evolution and relationships of
the heteromyid rodents with new forms from the
Tertiary of western North America. Ann. Carnegie
Mus. Nat. Hist., 24:73-262.
WOOD,A. E., ANDR. W. WILSON. 1936. A suggested
nomenclature for the cusps of the cheek teeth of
rodents. J. Paleontol., 10:399-391.
REPRODUCTIVE BIOLOGY OF THE RIO GRANDE CHUB, GILA PANDORA
(TELEOSTOMI: CYPRINIFORMES), IN A MONTANE STREAM,
NEW MEXICO
JOHN N. RINNE
United States Department of Agriculture, Forest Service, Rocky Mountain Forest and
Range Experiment Station, The Southwest Forest Science Complex,
2500 South Pineknoll Drive, Flagstaf, AZ 86001
The Rio Grande chub, Gila pandora, was first
reported and described from the Sangre de Cristo
Pass in the headwaters of the Rio Grande basin,
New Mexico (Cope, 1872). It commonly inhabits
pools in streams cool enough for trout, and often
uses undercut banks and brush for cover. Koster
(1957)
reported that spawning
occurs in "late
spring," with neither nest construction nor egg
care evident. Gila pandora is reported as a bait
(Miller, 1952) or forage fish, but Koster (1957)
suggested it might potentially compete with trout.
It has been suggested that the Rio Grande chub
is becoming rare in the Pecos basin (Minckley,
1980). Sublette et al. (1990) described populations in New Mexico as stable and reproducing
throughout most of their historic range.
The Rio Grande chub was encountered in large
numbers during research on grazing effects on
stream habitat and biota in an upper elevation
(>2,500 m) montane stream (Rio de las Vacas)
in northern New Mexico (Rinne, 1988). Because
ecological and life history information on the species is sparse, specimens of chub were retained
and preserved during 1985 to 1987 to define selected aspects of its reproductive biology. The
purpose of this paper is 1) to report the results
of analyses of these data and 2) compare it to
similar data for congeners.
The Rio de las Vacas is a montane stream
(elevation ca. 2,800 m) located on the Santa Fe
National Forest, Sandoval County, about 120 km
NNW of Albuquerque, New Mexico (Fig. 1).
Detailed descriptions of this riparian-stream area
are given in Rinne (1988) and Szaro and Rinne
(1988) and are summarized here. This third-order stream is affected by typical United States
Forest Service multiple-use management activities, including logging, recreation, road building,
and livestock grazing. The portions of the study
area that have been fenced to exclude grazing
have more abundant shrubby riparian vegetation,
such as willow (Salix sp.) and alder (Alnus sp.)
than grazed regions. Beaver (Castor canadense)
inhabit the area, and while damming of the stream
is common, it is not permanent because of annual
washouts by spring runoff. Streambanks are unstable in the grazed areas and fine sediment content of the stream substrate is greater in reaches
subjected to grazing (Rinne, 1988).
The Southwestern Naturalist
108
N
vol. 40, no. 1
TABLE1-Comparison of reproductive traits of male
and female Rio Grande chub (Gila pandora) in the Rio
de las Vacas, 1985-1987. Values are means (±SE).
All comparisons are significantly different (P < 0.01).
Cuba
24 km
Cuba
Study
Section
Albuquerque
Trait
Total length
(mm)1
Fish volume (ml)
Gonad (ml)
Color index
Gonadal index
Male
n = 79
109.70
15.80
0.38
1.30
2.15
±
±
±
±
±
1.6
0.69
0.03
0.05
0.18
Female
n = 105
117.50
21.80
1.16
1.50
4.84
± 2.5
+ 1.4
± 0.11
± 0.05
± 0.39
Range in total length = 67-140 mm in males, 52181 mm in females.
1 km
FLOW
FIG.1-Location of the Rio de las Vacasin northern
New Mexico. Sample areas are indicatedby shading.
In 1985, Rio Grande chub were collected during regularly scheduled summer (June and July)
sampling, with additional samples taken in
March, April, September, and October 1985 to
1987. Specimens were immobilized with a DC,
backpack electrofishing device, captured with
dipnets and immediately preserved in a 10% formalin-sugar solution to retain coloration. The
total lengths (TL) of preserved specimens were
measured, and fish volumes were estimated by
liquid displacement. Gonads were then removed
and their volumes similarly determined by liquid
displacement. Fecundity was estimated by removing ovaries and counting ova present in a subsample of 20 females collected in March and June
1985 with gonadal indices (see below) of 4.0 or
greater.
Presence and intensity of tuberculation and
breeding coloration on the body (1 = present; 2
= absent) and fins were noted relative to sex.
Variation in tuberculation was coded from 1 to
3 to delineate pronounced presence (1), weak
presence (2) or absence (3). Gonadal indices (GI)
were calculated by dividing gonadal volume by
fish volume and multiplying the resulting value
by 100. Data were analyzed by t-tests, analysis
of variance (ANOVA), and logistic regression.
Of the 184 Rio Grande chubs collected for
reproductive analyses, females were more abun-
dant (n = 105) than males (n = 79). Female chub
averaged significantly greater in both length and
volume (t-test, P = 0.01) than males (Table 1).
As is common in cyprinids, the presence of color
and its intensity was also significantly (P < 0.001)
more common in males than in females. Multiple
regression of color in chubs showed this trait related significantly (P < 0.01) to size and month
of collection. However, the regression model explained only about 25% of the variation in color
of chubs. By comparison, logistic regression produced a "best fit" model that included sex, month,
and gonad volume. The remaining two independent variables, fish volume and length, were not
significantly (P = 0.28 and 0.43) related to color.
The fitted model for chubs in the Vacas is: E(the
- 1.1176(sex) + .3480(month)
logit) = -3.0788
+ 1.4264(gonad volume), where the probability
of no color = expected E/(1 + expected E). This
model predicted the correct outcome 73.9% of the
time (136 of 184 specimens).
Difference in tuberculation on the body and
fins of male versus female chubs was not as marked
as was coloration (Table 2). Tubercles were more
pronounced on the caudal peduncle of males than
females and extremely more pronounced on the
anal and caudal fins of males.
As in most fishes, GI was significantly greater
(P < 0.001) in females than in males (Table 1).
ANOVA indicated significant differences (P =
0.001) in gonadal indices among sample dates for
both males and females (Table 3). If one uses
higher indices (>5.0) as an indicatoin of maturity, chubs reach maturity at about 90 mm, TL
(Fig. 2). Fecundity of the subsample of 20 female
chubs ranged from 1,366 to 6,322 ova, and av-
TABLE2-Comparison
of degree of tuberculation on
body and fins of male and female Rio Grande chub
(Gilapandora)in the Rio de las Vacas, New Mexico,
1985-1987. All values are means ± SE. * = P < 0.05;
** = P < 0.01.
Tuberculation
Body
Head
Caudal peduncle
Gular
Operculum
Pectoralfin
Pelvic fin
Anal fin
Caudal fin
109
Notes
March 1995
Male
n = 79
2.9 ±
2.9 ±
2.4 ±
3.0
3.0
3.0
3.0
2.0 ±
3.0 ±
0.03
0.03
0.10*
0.09**
0.02*
Female
n = 105
3.0
3.0
2.6 ± 0.07*
3.0
3.0
3.0
3.0
2.3 ± 0.01**
3.0*
eraged 3,362 + 366 (SE) ova. Regression analyses indicated only 10% of the variation in fecundity of chubs was explainable by gonad volume.
In contrast to Koster's (1957) observation that
the Rio Grande chub spawned only in spring,
chubs displayed an apparent bimodal spawning
pattern in the Rio de las Vacas (Table 3). Assuming that a mean GI greater than 5.0 and color
presence and intensity indicate reproductive activity, chubs have an extended spawning peak in
spring (March to June) followed by a briefer,
less marked autumnal (mean GI > 4.0; September to October) spawning event. Alternatively,
the GI peak in Autumn may represent egg development for the following spring's spawning.
The main discrepancy which contradicts this
bimodal pattern was mean GI development in
June 1985 versus June 1987. The lower mean
GI in both males and females in the temporally
asynchronous sample in June 1987 compared to
June 1985 is attributable to less volume and persistence of spring runoff in 1987. Conceivably,
the chub both commenced and terminated spawning earlier relative to streamflow in 1987. Further, very low flow conditions in June 1987 repressed mean gonadal development to low values
in both males and females compared to June 1985.
Little information is available in the published
literature on the reproductive biology of chubs of
the genus Gila in the southwest. Vanicek and
Kramer (1969) reported that roundtail chub in
the mainstream Green River spawned in spring
with rising water temperature and receding flows.
Using gonadosomatic index (gonad weight/body
weight), Neve (1976) reported a subspecies of
TABLE 3-Comparison of mean seasonal gonadal
indices of Rio Grande chubs (Gila pandora) in the Rio
de las Vacas, New Mexico, 1985 to 1987. Multiple
range test groupings of sample periods are indicated
by alphabetical denotation.
Male
Sample
date
n
March'
April
June
June
July
Sept
Oct
7
3
26
16
6
8
13
Female
X + SE
3.20
2.33
2.58
0.65
1.49
3.56
1.92
±
±
±
±
±
±
±
0.43c
1.18b
0.25c
0.19a
1.00b
0.59c
0.41b
n
5
5
36
24
5
16
14
X + SE
±
±
±
±
2.44 ±
4.04 ±
4.34 ±
5.40
3.30
7.43
2.46
1.17e
1.73c
0.87f
0.366
0.28a
0.39d
0.44e
1 All samples made in 1985 except for the second
sample listed for June and the sample for September,
which were made in 1987.
roundtail chub, G. robusta grahami described by
Rinne (1976), as spawning from January to
March in Fossil Creek, Arizona which was influenced by a thermal spring. Fecundity of the
total
roundtail chub in Fossil Creek (1,000-4,000
ova per female) was similar to the range of fecundity estimated for Rio Grande chub in the Rio
de las Vacas. Based on appearance of young in
collections, reproduction is listed as spring and
early summer for both the Yaqui (Gila purpurea)
and Sonora (Gila ditaenia) chubs (Minckley,
1973). Cross (1978) reported enlargement of testes of Virgin River roundtail chubs (Gila r. seminuda) in March.
20
16
12
INDEX
8
GONADAL
4
0
50
80
110
140
170
200
TOTAL LENGTHINMILLIMETERS
FIG. 2-Regression of gonad index on total length
of female chubs to delimit probable size at maturity.
Dashed lines are 95% confidence limits of means for
both fitted (lower two) and predicted (upper) regression lines.
110
The Southwestern
Neve (1976) reported that male roundtail chubs
in Fossil Spring, Arizona, developed small white
tubercles and an orange tinge at the base of the
fins. Female chubs in Fossil Creek also developed
"minor" tuberculation in the head region. Rinne
and Minckley (1970) list reddening on the fin
bases, jowls, and the lower body of male Gila
chub (Gila intermedia). Coloration on the fins and
body of other Gila has been described by Minckley (1973). Miller (1945) noted and described
breeding coloration of types of Sonora chub. The
axils of the pectoral and pelvic fins and the base
of the anal fin were described as brilliant Chinese
red. The brightest fish were orange on the sides
of the belly between the bases of the paired fins,
and although sexes were not separated, the
brightest fish were obviously males. Similarly,
coloration in the Rio Grande chub in the Rio de
las Vacas was present in both sexes, but was
significantly more common in males than in females (Table 1). McNatt (1974) reported prebreeding male Yaqui chub (Gila purpurea) as
"steely blue" in color and females as straw-yellow. Coloration was reported to be very intense
in the undescribed, now-extinct Monkey Springs
chub (Gila sp.).
LITERATURECITED
COPE,E. D. 1872. Report on the recent reptiles and
fishes of the survey collected by Campbell, Carrington, and C. B. Dawes. Preliminary report of
the U.S. Geological Survey of Territories, 1872.
U.S. Geological Survey, Washington, D.C.
CROss, J. N. 1978. Status and ecology of the Virgin
River roundtail chub, Gila robusta seminuda (Osteichthys: Cyprinidae). Southwestern Nat., 23:519528.
KOSTER,W. J. 1957. Guide to the fishes of New
Mexico. Univ. New Mexico Press, Albuquerque.
Naturalist
vol. 40, no. 1
McNATT, R. M. 1974. Re-evaluation of the native
fishes of the Rio Yaqui in the Unites States. Proc.
Ann. Conf. Western Assoc. Game and Fish Comm.,
54:273-279.
MILLER,R. R. 1945. A new cyprinid fish from southern Arizona, and Sonora, Mexico, with the description of a new subgenus of Gila and a review of
related species. Copeia, 1945:104-110.
-.
1952. Bait fishes of the lower Colorado River
from Lake Mead, Nevada, to Yuma, Arizona, with
a key for their identification. California Fish and
Game, 38:7-42.
MINCKLEY,
W. L. 1973. Fishes of Arizona. Arizona
Game and Fish Dept., Phoenix.
1980. Rio Grande chub. Pp. 170, in Atlas
of North American freshwater fishes (D. S. Lee et
al., eds.). North Carolina State Museum, Raleigh.
NEVE, L. C. 1976. The life history of the roundtail
chub, Gila robustagrahami, at Fossil Creek, Arizona.
Unpubl. M.S. thesis, Northern Arizona Univ.,
Flagstaff.
RINNE,J. N. 1976. Cyprinid fishes of the genus Gila
from the lower Colorado River Basin. Wassman J.
of Biol., 34:65-107.
1988. Grazing effects on stream habitat and
fishes: research design considerations. North Amer.
J. Fish. Mgmt., 8:240-247.
RINNE,J. N., AND W. L. MINCKLEY. 1970. Native
Arizona fishes: Part III: "Chubs." Arizona Wildl.
Views, 17:12-19.
SUBLETTE, J. E., M. D. HATCH, AND M. SUBLETTE.
1990. The fishes of New Mexico. Univ. New Mexico Press, Albuquerque.
SZARO,R. C., AND J. N. RINNE. 1988. Ecosystem
approach to management of southwestern riparian
communities. Trans. 53rd N. Amer. Wildl. and
Nat. Res. Conf., 53:502-511.
VANICEK,C. D., AND R. H. KRAMER. 1969. Life
history of the Colorado Squawfish, Ptychocheilus
lucius, and the Colorado chub, Gila robusta, in the
Green River in Dinosaur National Monument.
1964-1966. Trans. Amer. Fish. Soc., 98:193-208.