7222

• UCREFRP Catalog Number: 7222
• Author: Marsh, P. C. and J. E. Brooks
• Title: Predation by Ictalurid Catfishes as a Deterrent to Re-Establishment of Hatchery-Reared Razorback Suckers
• USFW Year: 1989
• USFW - Doc Type: The Southwestern Naturalist
• Copyright Material: YES

192 The Southwestern Naturalist vol. 34, no, 2
¦ 1984
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FIG. 1-Relationship between standard lengths (SL) of piscivorous flathead catfish and measurable
razorback sucker prey in stomachs of catfish from Gila River near Clifton, Arizona, during 21 to 23
September 1984 (squares), 13 to 15 September 1985 (circles), and 8 to 10 January 1986 (triangles).
4
0.95) smaller in 1985 than in 1984 and 1986, probably because razorback
suckers stocked in 1985 were smaller than those stocked in other years. Mean
size of catfish was similar among years (Table 1). There was no relationship
between catfish size and number of suckers eaten (r2 = 0.16, P > 0.20); mean
number of razorback suckers per catfish ranged among years from 1.1 to 2.3
and among individual catfish from 1 to 6 (Table 1).
Foods of catfishes in all years of study were comparable to those of small
samples of both species taken in summer 1984 prior to stockings of razorback
sucker. Flathead catfish then contained fish remains, including red shiner and
channel catfish, while channel catfish were omnivorous, consuming fishes and
a variety of aquatic insects and miscellaneous items (Table 2). These results
parallel those from other southwestern habitats (Marsh, 1981; Minckley, 1982)
and elsewhere (see reviews by Miller, 1966, and Carlander, 1969).
Both catfishes in the Gila River appeared stimu ated to unusually heavy
feeding by the sudden abundance of newly-stocked razorback suckers. Fre-
quencies of fish occurrence in catfish diets elsewhe e in the region scarcely
exceed 40% and usually are much lower (Marsh, 198 ;Minckley, 1982). The
suckers were presumably highly vulnerable to pred tion because they were
disoriented due to transport, stocking stress, and novels rroundings. They were
also presumably naive to predators (Minckley, 1983 other than occasional
piscivorous birds and human collectors under hatchery conditions, and generally
moved in mass. A comparable event involving other piscivores was recorded by
Keith (1969) after mass releases of juvenile walleye (Stizostedion vitreum vitreum)
SL (mm) Flathead Catfish