7428

• UCREFRP Catalog Number: 7428
• Author: Tyus, H. M.
• Title: Management of Native Warmwater Fishes of the Upper Colorado River.
• USFW Year: 1990.
• USFW - Doc Type: \
• Copyright Material: NO

The Green River supports at least two spawning aggregations of razorback
suckers. Ripe fish are routinely collected, but as elsewhere, young and
juveniles are not captured, suggesting that recruitment, if it occurs at all,
is to low to support the adult populations (Lanigan and Tyus 1989, Marsh and
Minckley 1989). Hypotheses for the lack of observed recruitment includes
predation of introduced fishes on the eggs, fry, and young razorback sucker
(Marsh and Langhorst 1988) and the loss of flooded nursery habitat (Tyus and
Karp 1989). Studies evaluating both of these problems are underway in the
Green River, and recommendations have been made for annual inundation of
seasonally-flooded lands that are used by the fish (Tyus and Karp 1991).
Colorado squawfish migrations have been observed for a hundred years,
and travels of hundreds of kilometers have been recently documented (Tyus
1990). Constructions of dams in the upper Colorado River basin, including
Flaming Gorge Dam on the upper Green River and Taylor Draw Dam on the White
River, have blocked passage of migrating Colorado squawfish, as evidenced by
their congregations below these obstructions prior to spawning season
(McDonald and Dotson 1960, Seethaler 1978, Martinez et al. 1987). However, no
passage facility has ever been tested or built for Colorado squawfish, and
these dams have not been fitted with fish passageways. Loss of the fish below
barrier dams, increased fishing pressure thus created, or attrition has,
sooner or later, disrupted Colorado squawfish migrations.
Stream passage for Colorado squawfish, although perhaps technically
possible, is in a very early stage of research and development. Construction
of passageways would perhaps best be accomplished in areas supporting active
Colorado squawfish migrations, however, such construction is unlikely because
of federal agency enforcement of provisions of the Endangered Species Act. If
passage is tested in locations where there are no fish migrations or fish to
use them, then new migrations would have to be established. Passageways must
also have the capability to pass not only adults, but younger life stages as
well, and in both directions. Retrofitting existing facilities would be very
costly, with no guarantee of success at this time.
Provision of new, or improvement of existing habitats, can only be
successful if ecological requirements of the fishes are met. This cha]lenge
is recognized in the Recovery Program, and it is stipulated that:(1) Testing
and implementation of management techniques will not be conducted or
potentially affect confirmed spawning and nursery areas; and (2) The genetic
integrity of wild populations must be protected when using hatchery-reared
experimental animals (USFWS 1987). There are obviously other stipulations that
could be added, including a need to develop adequate follow-up, and provide
for maintenance of habitats developed. Also, delineation and protection of
sensitive areas for all species must be a major priority.
Stocking of Rare Fish Species
In the past, fish culture was directed at supporting or restoring sport
fishing, not restoration of endangered fishes. Thus, there are many research
needs that remain to be answered regarding the use of hatcheries and stocking
programs in management of endangered fishes. Without habitat maintenance or
improvement, hatcheries provide temporary refuges for genetic material, and
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