7269

• UCREFRP Catalog Number: 7269
• Author: Pimentel, R. and R. V. Bulkley
• Title: Concentrations of Total Dissolved Solids Preferred or Avoided by Endangered Colorado River Fishes
• USFW Year: 1983
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: YES

598 PIMENTEL AND BULKLEY
TABLE 2.-Individual and pooled distribution data and chi-square analysis for total-dissolved-solid (TDS) concentrations
preferred by three Colorado River endangered fishes. Distribution of the fish in the experimental chamber was determined
at the end of 24 hours. Concentrations of TDS ranged from 270 mg/ liter in compartment 1 to 7,400 mg/ liter in
compartment 8. All compartments had a TDS concentration of 270 mgl liter in control experiments. Pooled treatment
and control experiments were compared to a hypothetical uniform distribution in the "goodness of fit" analysis.
Test for
Percent of fish in compartment independence Goodness of fit
Treatment N 1 2 3 4 5 6 7 8 X2 P X2 P
Colorado squawfish
Control' 90 8 12 23 23 7 12 13 11 12.8 0.066
1 30 0 43 37 7 7 3 3 0 22.8 0.003
II 30 0 63 17 13 3 3 0 0 35.9 <0.001
III 30 17 13 47 20 3 0 0 0 18.1 0.012
Pooled I-III 90 6 40 33 13 4 2 1 0 41.2 <0.001 122.1 <0.001
Bonytail
Control' 120 20 17 10 13 17 5 13 5 20.9 0.005
I 40 0 3 7 25 55 5 0 5 36.8 <0.001
II 40 0 0 0 23 45 15 17 0 36.3 <0.001
III 40 0 0 30 0 43 0 27 0 43.2 <0.001
Pooled I-III 120 0 1 13 16 47 7 15 2 61.0 <0.001 161.9 <0.001
Humpback chub
Control' 120 23 24 19 12 7 2 5 9 48.0 <0.001
I 40 13 0 33 13 10 15 13 5 27.8 <0.001
II 40 3 13 47 5 10 13 7 3 29.9 <0.001
III 40 5 33 35 20 7 0 0 0 17.0 0.017
Pooled I-III 120 7 15 38 13 9 9 7 3 32.2 <0.001 82.9 <0.001
' Pooled controls
trations available (Table 3). Humpback chubs
were intermediate with respect to both pref-
erence and avoidance, and their preference was
similar to TDS concentrations in the Green,
Colorado, and Little Colorado rivers.
TABLE 3.-Total-dissolved-solid (TDS) concentrations
preferred and avoided by three Colorado River fishes,
from pooled data. Concentrations of TDS were measured
as conductivity after 24 hours in the gradient device and
converted to mg1liter TDS by the equation mg1liter =
(Amhos conductivity - 618)10.68. Preferred TDS con-
centration is given as the range of concentrations over
the three replicates for the pooled modal compartment.
Temper-
ature
of
TDS TDS gradi-
preferred' avoidedb ent
Species (mg/liter) (mg/liter) (C)
Colorado squawfish 560-1,150 4,400 14-16
Humpback chub 1,000-2,500 5,100 12
Bonytail 4,100-4,700 560; 6,600 16-18
Mode of the pooled-treatment distribution.
b Concentration avoided by 95% of the fish.
Discussion
Both Staaland (1969) and Reynolds and
Thomson (1974) obtained results similar to ours
with this apparatus and concluded that the de-
vice gives reproducible results. However, we feel
best results come from weakly schooling fish.
For strongly schooling fish, more replications
are needed.
In our experiment, Colorado squawfish and
humpback chubs had TDS preferences similar
to the TDS in the Green and Colorado rivers,
but the bonytail preference was about four times
greater than that in the river system. The high
TDS concentration preferred by bonytails may
drop as the fish grow older. This TDS prefer-
ence of the young may be indicative of a habitat
preference for warm, shallow backwaters where
evaporative loss could greatly increase TDS
concentrations. Several researchers have found
ontogenetic changes in salinity preference for
larval and juvenile fishes tested in the labora-
tory (Houston 1957; Baggerman 1960; Mc-
Inerney 1964; Otto and McInerney 1970;
Reynolds and Thomson 1974). Reynolds and