7258

• UCREFRP Catalog Number: 7258
• Author: Rosenfeld, M. J.
• Title: Morphometry in Chubs of the Genus
• USFW Year: 1986.
• Copyright Material: NO

upon visual consideration of the nuchal hump and caudal

peduncle, but plotted as described above.

DISCUSSION

Significant character loadings indicate that chubs are distin-

guished by differences in two general body regions:

the head and

mid-body.

The two regions had different loading signs, indica-

ting op~osite variational trends.

Mid-body measurements are -

dete~minants of body depth.

Similarly, signTficant PC2 scores

for head-region characters tended to be depth measurements. As

body depth increases, the depth of the head decreases.

Signifi-

cant PC3 loadings for head characters entail horizontal shifting

in the relative positions of pOints defining these measurements,

i.e., these cistance measures were elongated or contracted

dependent on the specimen.

The large nuchal hump found in ~ertain Colorado River chubs is

~onsidered important in chub taxonomy (Miller, 1946).

Aspects of

hump size or shape have been quantified for species identifica-

tions (Smith et al., 1979), although measurements of this

structure have not resulted in clear discriminations (Valdez ~nd

Clemmer, 1982).

Measurements in this study did not directly

irvclve the problematical hump.

Rdther, it entailed those mostly

derived from constructing measurement trusses.

The hump appears

correlated with some of these measurements since peA I03dirgs for

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