7778

• UCREFRP Catalog Number: 7778
• Author: Tyus, H. M. and N. J. Nikirk
• Title: Abundance, Growth, and Diet of Channel Catfish,
• USFW Year: 1990
• Copyright Material: YES

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190

The Southwestern Naturalist

voL 35, no. 2

TABLE 1-Abundance of adult channel catfish and
other fishes in spring electrofishing collections, Green
and Yampa rivers, 1987 and 1988 (both years com-
bined).

Catch of channel catfish
%
Loca- Hours Total Per Total
tion' fished catch Total hour catch
Green River
A 28.3 211 1 0.03 0.4
B 16.0 370 1 0.06 0.2
C 12.5 331 30 2.40 9.1
D 23.4 550 33 1.41 6.0
E 21.2 298 8 0.38 2.7
F 54.8 1,299 17 0.31 1.3
G 17.0 865 187 11.00 21.6

Yampa River
DNM 23.3

19.64

10.6

2,173

231

] Locations given in Fig. 1. DNM = Dinosaur Na-
tional Monument.

the lumen. In this case, 2 years were added to the age
of the fish, and the back-calculated lengths at consec-
utive annuli were shifted 2 years to reflect the true
annual growth. A back-calculated length at age 1 of
>80 mm would then indicate that the first annulus
had been eroded, and a back-calculated length at age
2 > 150 mm indicated that both the first and second
annuli had been eroded. We made no further attempt
to validate our aging method because of the voluminous
literature on aging channel catfish from spines (re-
viewed by Carl ander, 1969).
Channel catfish were sorted into eight groups based
on the reach in which they were collected. Analysis-
of-variance (ANOV A) was used for comparing back-
calculated lengths at age 1,3, 5,7, and 9, for evaluating
condition factor (K) between reaches, and for evalu-
ating differences in mean lengths of fishes consuming
different foods.
Stomachs were removed from channel catfish col-
lected in the Green and Yampa rivers from May to
July 1987 and 1988. Consumed foods were recorded
for each stomach based on the following major food
categories: aquatic invertebrates, terrestrial insects, fish,
mice, vascular plants, algae and detritus. The number
of stomachs containing a food category and a resultant
frequency of occurrence (%) were reported. No effort
was made to determine food volume. Stomachs with
no food were reported as empty.
River discharge, water temperatures, and sediment
concentrations of the Green River were obtained from
U.S. Geological stream gauging stations at Green River
and Jensen, Utah (ReMilliard et aI., 1988). The effects

of river discharge and water temperatures on growth
of age 0 channel catfish were evaluated using simple
linear regressions.

RESULTS AND DISCUSSION-Abundance-Adult
channel catfish comprised 8.3'70 of the total catch
of fishes (n = 6,097, Table 1). Five species
amounted to 91.3% of the catch as follows: flan-
nelmouth sucker, Catostomus latiPinnis, (31.8'70);
carp, Cyprinus carpio, (29.6'70); bluehead sucker,
Catostomus discobolus, (16.2%); channel catfish
(8.3'70), and roundtail chub, Gila robusta, (5.5'70).
Highest catches of 19.6 and 11 channel catfish/h
were taken in the Yampa and upper Green rivers
(stratum G), the most rocky and turbulent (gra-
dient >2 m/km) sections, where they averaged
10.6 and 21.6'70 of the electro fishing catch, re-
spectively (Table 1).
Freshwater catfishes are not as susceptible to
electroshocking collections as are other species,
including suckers and minnows (Larimore, 1961;
Jacobs and Swink, 1982), and turbid conditions
of the study areas prohibited capture of fish not
visible at the water surface. However, angling
with baited hooks in the summer months sup-
ported the apparent preference of channel catfish
for rocky, high gradient canyon habitats; 34.5 h
of fishing in eddy habitats in canyons (lower
Yampa River and stratum G, Green River) pro-
duced 1.3 catfish/h (n = 46), and 36 h of fishing
in eddy habitats in sand and silt-laden sections
(strata E and F, average stream gradient 0.2 to
0.4 m/km, respectively) produced only 0.5 cat-
fish/h (n = 19). Layher and Maughan (1985)
also found that standing stocks of channel catfish
increased in higher gradient streams in Kansas.
Age and growth-Measurement of 604 small
channel catfish, collected in strata A to F in Oc-
tober 1979 to 1985, indicated that a length of
about 80 mm was maximum for the first year of
life (Fig. 2). This was confirmed by aging pectoral
spine sections taken from 45 small channel catfish
(average TL = 53.6 mm, range of 27 to 76 mm)
also collected in the Green River, because fish
<80 mm TL had no annulus present. Pectoral
spine sections from 88'70 of 361 larger channel
catfish collected in the Green and Yampa rivers
were given the same age by different technicians
and were used for age and growth comparisons.
Adjusted back-calculated lengths at consecutive
annuli are reported in Table 2. The catfish ranged
in length from 26 to 756 mm TL, with respective
ages of 0 to 22 years. About 2% of these (n = 8)