7048

• UCREFRP Catalog Number: 7048
• Author: Desert Fishes Council ‎(Edwin Pister, e.
• Title: Proceedings of the Desert Fishes Council
• USFW Year: 1991.
• USFW - Doc Type: Volumes XX and XXI
• Copyright Material: NO

Table 1. Selected morphological features of Rhinichthys osculus
thermalis and three nearby populations of R. o_ yarrowi. Mean counts
and (standard deviations) are given for lateral line (LL) scales and
pectoral fin (PF) rays. Number of individuals and (% of total) are
given for fish lacking pharyngeal teeth in at least one secondary row.
R. o. thermalis
Kendall Warm Spr.
R. o_ yarrowi
Duck Creek Green River Boulder Cr.
Number 50
LL scales 56.0 (4.7)*
PF rays 13.3 (0.1)
50
64.8 (3.9)
13.4 (0.8)
No. without 43* 0
teeth in one (86%)
secondary row
21
68.6 (3.5)
14.2 (0.9)
0
40
68.0 (4.2)
13.3 (0.7)
1
(3%)
* Significantly different (P<.05) from all R. oo. yarrowi populations
from the Green River, but not from Duck Creek or Boulder Creek. These
results are in general agreement with the earlier descriptions by Hubbs and
Kuhns (1937), except that the present pectoral fin ray counts are higher,
and the Kendall Warm Springs dace are not significantly different from
speckled dace of all sources. The most important finding is the difference
in pharyngeal tooth formulas, which have not previously been studied for
Kendall Warm Springs dace. Of 50 specimens examined, 43 (86%) lacked
pharyngeal teeth in _at.leas-t one of the secondary.rows, whereas this
condition was extremely rare (1 out of a total of 111) in speckled dace from
the three sources. Since pharyngeal tooth counts appear not to be thermally
labile during early development, this suggests a genetically based
morphological differentiation of the Kendall Warm Springs dace.
Critical Thermal Maxima
There was no significant difference in critical thermal maxima between
Kendall Warm Springs dace and speckled dace from Duck Creek, with both
acclimated to 27 C (Table 2). For the Kendall dace, this acclimation
Table 2. Critical thermal maxima of Rhinichthys osculus thermalis
and R_ o_ yarrowi.
Source and Mean length
Acclimation N in mm Mean CTM
Kendall, 27 C 14 43.1 34.8 (a)*
Speckled, 27 C 13 48.4 (a) 34.3 (a,b)
Speckled, 24 C 7 48.8 (a) 33.9 (b)
* Common letter indicates P>.05 (Newman-Keuls)
temperature approximates the lower limit that might be experienced at any
time in the thermal spring creek. The CTM values for these dace acclimated
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