9595 ‎(2)‎

• UCREFRP Catalog Number: 9595
• Author: CRCT Task Force.
• Title: Conservation Agreement and Strategy for Colorado River Cutthroat Trout ‎(Oncorhynchus clarki pleuriticus)‎ in the States of Colorado, Utah, and Wyoming.
• USFW Year: 1999.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

cutthroat trout is classified as a sensitive species by Regions 2 and 4 of the USFS and by the BLM.

The basis for any status determination relies on the most comprehensive and up-to-date
assessment of existing populations. Given the ongoing conservation actions being implemented
through existing plans in Colorado, Wyoming, and Utah, which included inventories of known and
"new" CRCT populations and further morphomeristic and genetic tests for relative purity, past status
assessments (e.g. Young et al. 1996) are dated and new information is available. During the spring
of 1998, the Coordination Committee instructed agency biologists to compile this information on
existing CRCT waters in their areas as a first step in determining the numbers of pure, viable
populations within the tri-state area.

The CRFWC Committees agreed that most waters within the historic range are potential
CRCT waters, and developed an electronic database to hold, for all waters, data which the
Committees agreed are important in evaluating the rangewide status of CRCT. The data available
as of July 1, 1998 are presented as Appendix A. This database may be queried on the basis of one
or several of these data points to generate range-wide listings of waters reflecting many different
perspectives. The baseline database contains information on stream miles or lake acres occupied
by each populatiol1; genetic purity rating, numbers ofCRCT > 150 rom (6 in), type(s) ofbarrier(s),
type(s) of other salmonid(s) present, CRCT stocking history, and limiting habitat factors.

The numbers of, and stream mileage or lake acreage occupied by, conservation populations
of CRCT with genetic purity ratings ofB, B+, A- or A totaled 161 in a minimum of 524 stream
miles and 12 in 601 lake acres (Table 1). These results show pure and essentially pure populations
of CRCT are still represented in many stream drainages across the three states. Though the bulk of
the existing populations are found in only five of the 14 geographic management units (GMU), some
pure or essentially pure populations are present in every GMU, and provide a potential to maintain
and enhance the genetic diversity of this subspecies.

The assessments contained herein have been influenced by the approach that each state used
to determine and designate the presence of hybrids within populations. Within Colorado and
Wyoming the state management agencies use a hybrid classification scheme that incorporates
meristic, morphometric, and molecular characters to represent the range of hybrid variability.
Within Utah, their interagency conservation team has adopted an approach that ranks hybrid
populations based on historic stocking records as well as meristic, morphometric, and molecular
characters. Both of these approaches provide a mechanism for determining the value of an
individual population for conservation efforts based on the degree that individual fish within it may
be hybridized.

There is still some uncertainty about the numbers and status of remaining populations of
CRCT. The number of populations that ultimately should be managed for the long-term
conservation of this subspecies, therefore, exceeds the 173 populations included in this status
assessment (Appendix A). Pending completion of Utah's index approach to rating genetic purity,
over 200 populations in that state have not been evaluated for genetic purity. It is feasible that the
number of conservation populations currently in Utah will expand to equal or exceed levels observed

March 1999

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