|
<br />i
<br />
<br />.'
<br />,
<br />
<br />~
<br />'.'
<br />
<br />Distribution
<br />
<br />.,
<br />..,
<br />
<br />The historic distribution of the humpback chub is unclear, because of the lack of historic
<br />collections and confusion in taxonomy and nomenclature with the other species of chubs; Le"
<br />roundtail chub and bonytail (Valdez and Clemmer 1982), Bas~ on historic records and agency
<br />reports, the species was probably once distributed throughout most canyon regions of the
<br />Colorado River Basin, and is presently found as six populations in the states of Colorado, Utah,
<br />and Arizona, including Black Rocks, Westwater Canyon. Cataract Canyon. Desolation/Grey
<br />Canyon, Yampa Canyon, and Grand Canyon (Valdez and Clemmer 1982), Based on early capture
<br />records, it was extirpated from Flaming Gorge (Gaufin et ai, 1960), Lodore Canyon. Whirlpool
<br />Canyon, Split Mountain Canyon (Holden and Stalnaker 1975), lower Cataract Canyon (Valdez
<br />and Williams 1993), Debeque Canyon (Valdez and Clemmer 1982), and regions of Grand Canyon
<br />(Valdez and Rye11995),
<br />
<br />~~'
<br />
<br />The Grand Canyon population is the only successfully reproducing HBC population in the lower
<br />Colorado River basin (Kaeding and Zimmennan 1983; Valdez 1995), The largest population of
<br />humpback chub is in Grand Canyon. where in 1990-1993 fish were distributed as nine
<br />aggregations in 190 miles of the Colorado River (RM 30-220; i,e" RM=river miles or distance
<br />downstream from Lees Ferry) and in the lower 9 miles of the LCR (Valdez and Rye! 1997, Totals
<br />of3,750 adults (<!200 mm TL) were estimated in the mainstem in 1990-93 (Valdez and Ryel
<br />1997), and 4,602 adults in the LCR in May 1992 (Douglas and Marsh 1996), Since the LCR
<br />estimate was made during spawning season in May, this estimate includes fish from the rnainstem,
<br />and so, total numbers of adults in Grand Canyon cannot be derived as the sum of the two -
<br />estimates.
<br />
<br />.~.
<br />
<br />"
<br />t~;
<br />
<br />~
<br />
<br />>:-
<br />~~
<br />
<br />~,
<br />(, r',
<br />('.
<br />:;,"..
<br />
<br />Humpback chub were held in hatchery facilities in the late 1970's and early 1980's, and in
<br />December 1981, the only release of hatchery-reared fish was made in Cataract Canyon. Utah,
<br />when the Service released 7,600 age I fish that were progeny of Black Rocks parents (U,S, Fish
<br />and Wildlife Service 1990), Except for small numbers of individuals being used for laboratory and
<br />experimental purposes, there are presendy no humpback chub brood stocks in any hatchery
<br />facility,
<br />
<br />
<br />C~:
<br />;'E"
<br />
<br />?t~
<br />I.e.:'!
<br />_:!,',
<br />!-':>:
<br />;::"';
<br />
<br />Movement
<br />
<br />.~~
<br />",-,,~
<br />W,;;
<br />~
<br />'~:.~
<br />ii'
<br />.t;:'"
<br />
<br />Adult humpback chub exhibit a high degree of spatial fidelity for specific river locales,
<br />Movement of 69 radio tagged adults tracked in Grand Canyon during 1990-92 (mean, 1.49 km;
<br />range, 0-6,11 Ian; 30-170 d; Valdez and Ryel1997) was similar to that reported for the species
<br />from Black RocJcs. Colorado, by Valdez and Clemmer (1982) (mean, 0,8 Ian; N=8 radio tagged
<br />adults) and by Kaeding et ai, (1990) (mean, 1.4 Ian; N=10 radio tagged adults),
<br />
<br />, ~: "',
<br />
<br />x
<br />
<br />Habitat
<br />
<br />Humpback chub prefer deep, swift water with rocky substrate, Young occupy srnal1, quiet
<br />
<br />16
<br />
|