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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The Southwestern Naturalist

vol. 35, no. 2

194

TABLE 2-Average calculated total lengths at each annulus for channel catfish in the Green and Yampa
rivers, 1979 to 1988. n = number of fish in which the respective annulus was present in pectoral spine section
(45 age-O catfish collected in 1988 not included).

Average total length at annulus formation'
YC2 2 3 4 5 6 7 8 9 10
87 53
86 45 128
85 31 110 167
84 63 120 171 220
83 65 109 177 203
82 64 119 169 212 246 225
81 70 115 163 202 236 260 282
80 66 111 156 192 224 252 275
79 74 121 166 201 233 261 282 299
78 67 119 165 201 226 251 272 290 304
77 65 116 170 209 239 263 286 308 321 343
76 61 110 166 215 249 276 301 321 341 361
75 70 109 157 196 240 273 295 315 337 354
74 103 168 193 225 258 285 307 323 336
73 72 115 154 188 223 255 282 299 319 344
72 119 178 229 273 307 335 353 373 392
71 96 135 176 201 252 296 325 353 382
70 138 166 216 250 279 299 329 343 369
66 175 239 254 292 322 371 429 472
X 63 116 165 202 234 260 283 305 322 352
SE 1.7 1.2 1.4 1.6 1.7 1.8 2.0 2.5 3.4 4.0
n 70 260 303 290 277 264 224 169 131 89

1 Numbers rounded.
2 YC = year class; 66 to 87 represent years 1966 to 1987.

catfish stocks at these locations intermingled sig-
nificantly or that factors other than physical hab-
itat were limiting growth. Although channel cat-
fish may display extensive movement in streams
(Hubley, 1963), we believe that growth was re-
duced by a limited resource base, short growing
seasons, and low water temperatures.
Diet-Most of the 755 stomachs inspected con-
tained food (76.2%), but 23.8% were empty
(Yampa River, 21.75%, n = 75; Green River,
25.6%, n = 105). Aquatic invertebrates were
present in 31 % of stomachs containing food (n =
575); 28% contained vascular plants, including
horsetail, Equisetum sp. (Sphenopsida), juniper
berries, seeds, twigs, and leaves; 22% contained
terrestrial insects; 10% contained algae, detritus,
and miscellaneous items; 7% contained fish; and
1.5% contained mice (Table 3). These foods are
similar to those in other locations (Bailey and
Harrison, 1948; Davis, 1959; Carlander, 1969;
Moyle, 1976).

Channel catfish utilized different foods de-
pending on size (and presumably age), river
section, and season. Although there were some
differences in type of foods selected by different-
sized fish in both the Green and Yampa rivers,
many of these differences were not significant
when the rivers were combined. The only size-
specific difference in diet was between individuals
consuming vertebrates and individuals consum-
ing other foods (Table 3). Terrestrial insects (e.g.,
Mormon crickets) and vascular plants (e.g.,
horsetails) were relatively abundant in the Yam-
pa and Green rivers in Dinosaur National Mon-
ument in late spring to mid-summer and were
heavily utilized by channel catfish (Tyus and
Minckley, 1988). However, these items are gen-
erally scarce in the lower Green River. An algae,
Cladophora sp. (Clorophyta), transported into the
Dinosaur National Monument area of the Green
River from the clear tailwaters of Flaming Gorge
Dam, was a common food item of channel catfish