7083

• UCREFRP Catalog Number: 7083
• Author: Ferriole, S.
• Title: Wildlife Resource Information System
• USFW Year: 1988.
• USFW - Doc Type: Humpback Chub Mapping Criteria for the Colorado, Dolores, Gunnison, Green, White, and Yampa Rivers.
• Copyright Material: NO

Spawning ar,d Egg Survival
Little is known about natural reproduction of humpback chubs
partly because the species spawn during spring runoff when sampling
conditions are poor {Valdez et al. 1~J82). Humpback chub spawning
sites have not been located (L. Kaeding, USFWS, pers. comm.}. The
species-may spawn in pockets of rubble and gravel within Westwater
Canyon and Black Rocks (Miller et al. 1982c) or on submerged cobble
bars near the upstream end of Brlack Rocks (Valdes and Nilson 1982).
Some humpback chubs may spawn just outside the deepwater areas of
Black Rocks (Archer et al. 1985).
Humgbaek chubs in the Little Colorado River probably spawned
during April and May in 1981 (Kaeding and Zimmerman 1983)..
Suspected spawning at Black-Rocks in 1981 to 1984 ranged from
. mid-May to end of July, and water temperatures ranged from 11.5 C to
23 C (Valdez and Nilson 1982, Archer et al.. 1985). Optimum egg
survival is at 20 C (Bullcley et al. 1982, Marsh 1985). Incidence of
abnormal fry is lowest at 2D C (Marsh 1985), and survival of fry is
greatest at 21-22 C (Hamman 1982).

Reasons for Decline and Limiting Factors
Decline of humpback chub populations is attributed mainly to
loss of Habitat caused by construction and operation of Flaming
Gorgcr and (;1Fn Canyon dams, and perh~~ps Hoover Dam (liSFlti'S 1J7J).
Reservoic•s and their cold tailwaters are nut suitable for
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