3017

• UCREFRP Catalog Number: 3017
• Author: Suttkus, R. D. and G. H. Clemmer.
• Title: The Humpback Chub,
• USFW Year: 1977.
• Copyright Material: NO

NUMBER 1, 1977

and others occur over inter-spaces between the scales.
This is also true of the distribution of predorsal tubercles
in the female. There are a few tubercles on the ventral
portion of the head of the male. There are a few on
the isthmus, rami or lower jaws, on the branchiostegals,
and a few on the ventral portion of gill membrane.
There are well developed tuberculate ridges on the ex-
posed margins of the scales of breast patches (Figure 22) .
There are elevated blunt points along these tuberculate
ridges as though a row of tubercles became fused at their
base. There is a single row of tubercles on the posterior
upper margin of the first pectoral fin ray and double
rows proximally on the second, third, fourth, fifth and
sixth pectoral fin rays. As the rays branch distally the
rows of tubercles also branch to some extent. There are
a few tubercles on the seventh, eighth, and ninth pectoral
fin rays. There are developed tubercles on second, third,
fourth and fifth pelvic fin rays. The number of tubercles
diminishes from the third to the fifth pelvic fin rays.
Because of the extensive lateral area of the body from
which the thickened epidermal layer has been lost
through handling, the precise extent of tuberculation on
the lateral scales cannot be ascertained. We assume there
was an elongate tuberculate area extending from the
humeral region posteriorly to the region below the mid-
dle of the dorsal fin. There are a few lateral line scales
with a few small tubercles along their exposed margins,
but no scales below the lateral line appear to have any
tubercles, thus the major portion of the tuberculate lat-
eral scales is in the intervening area between the lateral
line and the small embedded dorsal scales. The tubercles
are situated along the exposed margins of the scales and
are larger and more numerous on the anterior scales in
the described patch. The number of tubercles per scale
margin varies from one to seven.
The larger female taken with the male described above
also has some tuberculation. There are very small tuber-
cles on anterior pectoral fin rays but none on the pelvic
fin rays. The tuberculate ridges are developed on the
margins of the scales of the breast patches.
Three of the seven specimens of sample no. 76-II ex-
amined from the July 25-26, 1967 collection obtained
from just below Glen Canyon Dam by Stalnaker, Camp-
bell, Holden, and Joe Stone have some tuberculation.
These male specimens (metal strap tag nos. 2761, 2763,
and 2771) are presently housed at the Ft. Collins, Na-
tional Fish and Wildlife Laboratory. Specimen number
2761 has slightly developed tubercles on the second, third
and fourth pectoral fin rays. There were no tubercles
on the head or the pelvic fin rays. Specimen no. 2763
has moderately developed tubercles on the second to fifth
pectoral fin rays and the second to fifth pelvic fin rays.
There are a few tubercles on the first ray of the right
pectoral fin and few tubercles on top of the head on the
interorbital area. Specimen no. 2771 has a few tubercles
on the second, third and fourth pectoral fin rays, none
on the pelvic rays, a few on the top of head, tip of the
snout and upper part of the opercle but none on the
breast patches of scales.

5

Another series (sample no. 67-12) taken from Powell
Reservoir during 1967 by Rod Stone and Kent Miller
does not have a precise date, but by placement between
sample no. 67-II and sample no. 67-13 which was col-
lected a few days after the Glen Canyon Dam collection
(cited above), the implied date for sample no. 67-12 is
26 or 27 of July, 1967. The four male specimens (metal
tag nos. 2736, 2737, 2739, and 2741) examined had slight
to extensive tuberculation. The tuberculation was simi-
lar to that described above. Specimen no. 2737 has the
best development of breeding tubercles on the fins.
There is a single row on the first pectoral ray and a
single row proximally to four rows distally on the second
to the seventh pectoral ray. There are no tubercles on
the first pelvic ray. On the second to the sixth pelvic
ray there is a single row of tubercles proxim.ally which
soon divides into two rows, one on each branch, and then
each of the two rows divide to form four rows and then
into eight rows n,~ar the distal tips of the rays. There are
a few extra tubercles suggesting the beginnings of divid-
ing into sixteen rows of tubercles at the very margin of
the fin. The breast patches of scales have tuberculate
ridges on their margins. There are approximately fifteen
diagonal rows of these tuberculate scales. There are rela-
tively larger tubercles scattered over the top of the head
and smaller ones extending posteriorly over the surface
of the hump. There is a progressive decrease in number
of tubercles, and they occur no farther than about two-
thirds the way toward the dorsal fin. Tubercles on the
head extend laterally and ventrally over the upper two-
thirds of the opercle and the upper third of the cheek.
There is a hiatus on the mid-cheek area. The scattering
of tubercles on the ventral surface of the head extends
laterally and dorsally on to the lower third of the cheek.

The male specimen with metal tag no. 2736 is not as
tuberculate on the fins as no. 2737 but has tubercles on
the margins of the lateral body scales. The number of
tubercles per scale ranges from one to five. This speci-
men has relatively large tubercles on the top of the head,
and the smaller tubercles extending over the hump are
scattered all the way to the dorsal fin. There are tuber-
cles on the upper lip, chin, rami of the lower jaws and
on the branchiostegals. The tuberculate ridges are de-
veloped on the scales of the breast patches. Three of the
five female specimens examined (metal tag nos 2734,
2735 and 2740) have tubercles. Small tubercles are scat-
tered over the top of the head and extend back over the
nuchal hump toward the dorsal fin. Some tubercles are
present on the pectoral fin rays and one specimen has
some tuberculate ridges developed on the breast patches
of scales. None of the females have any tubercles on the
ventral side of the head, on the pelvic fins or on the lat-
eral body scales.

Reproduction

The males with extensive tuberculation described
above seem to have fully developed testes. Of the five
females studied (metal tag nos. 2732, 2734, 2735, 2738,