8155

• UCREFRP Catalog Number: 8155
• Author: Minckley, W. L.
• Title: Executive Summary
• USFW Year: 1985.
• USFW - Doc Type: Native Fishes and Natural Aquatic Habitats in U.S. Fish and Wildlife Service Region II West of the Continental Divide.
• Copyright Material: NO

upper Colorado River basin (Valentine 1983). Tyus (1985) expressed concern
that these stocKings may result in disruption of natural homing or other
behavioral features of the species in that area.

Reintroductions into presumably suitable habitats in the lower basin
ha\Je been dela;/ed b;/ pol itical concerns, but were commenced in summer 1985
on an experimental basis in the Verde and Sal t rivers, Arizona. Other
habitats under consideration include the lower Colorado River mainstream
(Category II or III) and upper Gila River (Category I, but of relativel;
3mall size). A conservati\.'e approach is recommended to reintroduction and
re-establi:hment of this native predator in natural streams. Large
habitats for this and other big-river species are at a premium in the lower
basin, and presence of squawfish may be counterproductive to recovery
efforts for other fishes such as bony tail or woundfin. Prel iminary data on
razorback sucKer already indicate substantial predation by non-native
fishes such as green sunfish (LeDomis cyanellus) and flathead catfish
(Py1odictis 01 ivaris), channel catfish, and others, on newly introduced
stocks (Brooks ~ Ai. 1986).

HeavY predation on newly-stocked squawfish by non-native species may
also be anticipated, so stocl<ing sites for fry, fingerling, and/or
juveniles should be carefully selected or prepared prior to reintroduction
attempts. Perhaps onlY juvenile stocKing should be attempted in order to
avoid at least some of this predation pressure. Post-stocKing movements by
razorbacK sucKer are furthermore predominatelY downstream, so
recommendations were to i.ntroduce that species high in the selected
watersheds (BrooKs ~ Jl. 1986). This may also be true for Colorado
squawfish. If relatively large squawfish are available for stocKing,
radiotagging would be a valuable adjunct to subsequent monitoring and study
of the species.

Consideration of habitats other than natural streams that are or may
be made available for management of big-river fishes of the lower Colorado
River system are provided by MincKley (1986) and summarized in Sedler: n:
(pp. 102-103).

Bonyhi1, ~ eleQans Baird and Girard, 1853a (Map 8)

Historic occurrence: widespread. Abundance: common to scarce.
Geographic distribution: endemic to larger streams of Colorado River basin
(Smith ~ Ai. 1979; Holden 1980a). Status: endangered. Reasons for
decl ine or listing: basically unKnown - habitat loss (de1tJatering of lower
portions of major streams in lower basin); habitat modification (direct and
indirect effects of impoundment, channel ization, diversion, and re~ulation
of discharg~s) i hybridization with humpbacK and roundtail chubs, due in
part to factors Just given and to increasing rarity in the system (Hubbs
1 955, Sm i HI tl ~. 1 9(9) j and p 0 s sib 1 e i n t era c t ion s 1...1 i t h non - n .:0. t i v e
SP e c : e s .

A ma.:cr d:-f-f;cuity in ,je.:o.ling i..\.lith historical datO; on this spe,::es \::
1 0 C a 1 use of the n am e "b c n.. ~ 2. i 1" f 0;- a 1 m 0:: t a. n:- G i 1 2 : nth e 1 QI.~ ere c ' or 3..j:,
River b.asln. One is hard pres:ed to s.eparate !oun(~ta:l3.n.j true bon/tO;il
rec~rds, especially since they were broadly S/mpatric in the system.
DistriblJtic.n d t,c,nytail in the IQl..ller Color.ado Ri'-Je:. basin nonetheless

42.