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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196 The Southwestern Naturalist vol. 35, no. 2
TABLE 3-0ccurrence of food items in channel-catfish stomachs containing food, Green and Yampa rivers,
1987 and 1988 (n = number of stomachs).
Fish total length (mm)
Food items n % Average Range SD
Mice
Green River 1 0.3 721
Yampa River 9 2.5 407 339-480 49.6
Fish
Green River 18 6.2 443 264-756 151.7
Yampa River 26 7.7 398 261-521 64.8
Terrestrial insects
Green River 60 21 291 100-702 83.5
Yampa River 87 24 333 231-502 60.2
Aquatic invertebrates
Green River 95 33 313 164-546 61.6
Yampa River 108 30 329 157-502 58.9
Vascular plants
Green River 75 26 300 100-702 86.0
Yampa River 107 29 338 160-502 64.5
Algae, detritus
Green River 42 14 354 210-546 71.5
Yampa River 26 7 308 147-470 76.3

eludes such camp garbage as rice, corn, potatoes,
chicken bones, onion, broccoli, peas, noodles, fat,
cheese, and charcoal) reflects omnivorous feeding
(and scavenging behavior), as noted by others
(Bailey and Harrison, 1948; Davis, 1959).
There is little documentation that the prolif-
eration of the introduced channel catfish has has-
tened the deeline of rare and endangered Colo-
rado River fishes in the Green and Yampa rivers.
However, this species has a potential for adverse
impacts by directly preying on the native fishes
and by competing with them for food and space.
Other studies have shown that channel catfish
can negatively impact native Colorado River fish-
es (Marsh and Langhorst, 1988; Marsh and
Brooks, 1989). Large numbers of channel catfish
in canyon habitats of the Green and Yampa rivers
and their omnivory suggested that the fish could
reduce habitat and food availability for other fish-
es. Negative interactions between channel catfish
and the native fishes (e.g., Colorado squawfish,
Ptychocheilus lucius; roundtail chub; humpback
chub, Gila cypha; razorback sucker, Xyrauchen
texanus; and speckled dace) are suggested by a
common use of some foods and habitats (Tyus

and Minckley, 1988) and by predation on the
native fishes (Kaeding and Zimmerman, 1983;
Marsh and Langhorst, 1988; Marsh and Brooks,
1989; K. L. Coon, in litt.). In addition, records
of Colorado squawfish with channel catfish lodged
in their throats (McAda, 1983; Pimental et al.,
1985; E. J. Wick, pers. comm.) are further in-
dication of an adverse impact of this introduced
catfish.
It has been suggested that conditions for the
endangered Colorado squawfish might be en-
hanced in the Colorado River by elevating mean
river temperatures (Kaeding and Osmundson,
1988). We suggest that warmer water tempera-
tures and a longer growing season may exacerbate
adverse interactions between channel catfish and
endangered fishes. Andrews and Stickney (1972)
noted that food conversion of channel catfish in-
creased as the water temperature was warmed 22
to 30oC. If warmer temperatures resulted in bet-
ter growth and larger size of channel catfish, their
piscivory on native fishes would presumably in-
crease.
Channel catfish were abundant and widely dis-
tributed in the Green and Yampa rivers, partic-