7229

• UCREFRP Catalog Number: 7229
• Author: Kaeding, L. R. and M. A. Zimmerman
• Title: Life History and Ecology of the Humpback Chub in the Little Colorado and Colorado Rivers of the Grand Canyon
• USFW Year: 1983
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: NO

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Table 1. Sources of information and assumptions used in construction
of the suitability index graphs. "Excellent" habitat for the white
sucker was assumed to correspond to an SI of 0.8 to 1.0, "good" habitat
to an SI of 0.5 to 0.7, "fair" habitat to an SI of 0.2 to 0.4, and
IIpoor" habitat to an SI of 0.0 to 0.1.

Variable

Assumption and sources

V1

Although white suckers can tolerate a wide range of turbidities,
clear waters (< 50 JTU) are considered excellent (Raney and
Webster 1942; Pflieger 1975). Waters of 50 to 150 JTU are good
to fair depending on the range of turbidity variability. Rivers
exhibiting constant turbidities are more conducive to stable,
wide spread white sucker populations than rivers which have
widely variable turbidities even if moderate (Muth pers. comm.
1983). High turbidities are judged to be fair to poor depending
on the variability and length of time a habitat is turbid because
reduced populations have been reported in turbid waters (Muth
pers. comm. 1983; Pflieger 1971).

V2

The pH ranges which cause population declines or result in
slower growth are suboptimal (EIFAC 1969; Beamish 1972, 1974).
Levels of pH which allow maximum growth and reproduction are
optimum (EIFAC 1969; Trojnar 1977). It is assumed that frequent
pH fluctuations are suboptimum.

Dissolved oxygen levels which are low enough to cause white
suckers to avoid the area (2.4 mg/l) (Dence 1948), or are in-
adequate for reproductive success (s 1.2 mg/l), or decrease
growth (< 2.5 mg/l) (Siefert and Spoor 1974) are poor. Dissolved
oxygen levels ~ 6 mg/l are generally considered optimum and D.O.
levels in which white sucker populations can be successfully
maintained, reproduce, and grow would be judged as at least fair
to good.

V3

V4

Temperatures which correspond to optimum growth and activity are
considered excellent (Horak and Tanner 1964; Reynolds and
Casterlin 1978). Temperatures which are lethal are judged poor
(Brett 1944; Carlander 1969; McCormick et al. 1977). White
suckers, when acclimated, can survive a wide range of tem-
peratures when the temperature extremes are common to the area
and seasonal. These temperatures are rated poor to fair
(Thompson and Hunt 1930; Minckley 1963).

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