7327

• UCREFRP Catalog Number: 7327
• Author: Johnson, J. E.
• Title: Status of Endangered and Threatened Fish Species in Colorado.
• USFW Year: 1976.
• USFW - Doc Type: T/N 280,
• Copyright Material: NO

Their threatened species list for fish includes:
Scientific Name Common Name
5. Salmo clarki stomias Greenback cutthroat trout
6. Salmo clarki virginalis Rio Grande cutthroat trout
7. Salmo clarki pleuriticus Colorado cutthroat trout
8. Hybopsis aestivalis tetranemos Arkansas River speckled chub
9. Etheostoma cra ini Arkansas darter
10. Etheostoma nigrum nigrum Central johnny darter
11. Etheostoma spectabile pulchellum. Plains orange throat darter
Thus there is some confusion as to the status of several of these
species and in fact even the taxonomy of some is in question. It is
the belief of this office that all of the above species, on both state
and federal lists, are existing at reduced population levels within
the State boundaries, and all but the last four are truly in trouble
as a biological species or subspecies. The last two darters (E. ni rum
and E. spectabile) are widespread throughout their native range, and
reach their periphery in eastern Colorado streams (Hubbs and Lagler,
1970). The two Arkansas River endemics (E. cragini and H. aestivalis)
are also found in Kansas and Oklahoma streams but only in scattered
localities (Cross, 1967). Both are in need of further study before
any conclusions concerning their actual status as a biological species
is determined. It is believed that the Fish and Wildlife Service will
eventually move many of the species now classified as endangered over
to threatened species status because of the extreme limitations on any
management plans for endangered wildlife. Most of the declining wild-
life populations result from nonspecific disruption of their habitats,
and "hands on" management is necessary to correct these changes. The
threatened designation provides this freedom.
What follows is a general review of the status of those species known
to be existing at greatly reduced numbers in Colorado waters, some
reasons for their decline, and BLM's potential input into their survi-
val.
I. Trouts
All four recognized cutthroat trout subspecies in Colorado are part
of the highly variable gene pool of Salmo clarki. Although there is
still considerable debate as to the authenticity of these and several
other subspecies of cutthroat trout, most authorities agree S. clarki
has formed isolated populations in headwater streams of major drainages
in Colorado, Wyoming, New Mexico, Utah, California, and Oregon. The
questions of degree of isolation and differentiation account for the

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