8121

• UCREFRP Catalog Number: 8121
• Author: Williamson, J. H. and R. S. Wydoski.
• Title: Genetics Management Guidelines.
• USFW Year: 1994.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

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(Barker 1989). The Program philosophy, mission, and goals regarding genetic
' management of the endangered fishes are based on the recognition that stocks
or local self-sustaining populations must be considered the operational unit
in the recovery effort. Such endangered fish stocks may contain unique
' genetic attributes that allowed these endemic Colorado River fish species to
evolve and occupy habitats in the Upper Colorado River Basin that are-in the
northernmost part of their historic ranges (Philipp et al. 1986, 1993).
' A. Criteria for Identification and Characterization of Endangered Fish
Stocks. A stock is defined as a randomly breeding group of individuals
that has spatial, temporal, or behavioral integrity from other randomly
breeding groups of that same species (Kutkuhn 1981). This definition of
stock applies to multiple stocks within an individual river or a single
stock comprising fish from various rivers in the upper basin (Philipp et
' al. 1993) that sustain a Hardy-Weinberg equilibrium of unique genotypes
in stable stocks (Booke 1981). The biological uniqueness resulting from
isolation or geographic separation is an evolutionary one and such stocks
have been referred to as "evolutionary significant units" (Dizon et al.
' 1992).
All available information (i.e., distribution and abundance, behavior,
' migration, phenotypic information, and genotypic information; Dizon et
al. 1992, Ihssen et al. 1981) were considered among the criteria used to
identify and characterize endangered fish stocks in the upper basin.
Behavior and physiology of a stock may be important to survival in a
' particular environment (Larkin 1981). The criteria used to identify and
characterize endangered fish stocks in the Upper Colorado River Basin
(Wydoski 1994) were:
' 1. Geographic Distribution and Abundance. The basic criterion used to
separate endangered fish stocks was distribution and abundance of
' each species in the upper basin. Some disjunct stocks are
geographically separated from others and do not appear to exhibit
interchange between the stocks. For example, the humpback chub is
found as relatively small concentrations of fish that are widely
' separated and confined to short reaches of deep canyon areas (Valdez
and Clemmer 1982; Tyus and Karp 1989; Tyus and Karp 1991).
' 2. Identified or Suspected Spawning Sites. All major tributaries in the
Upper Colorado River Basin have been sampled to determine the
distribution and abundance of endemic and introduced fishes (Bestgen
1990; McAda et al. 1993; Miller et al. 1982; U.S. Fish and Wildlife
' Service 1990a, 1990b, 1991). Spawning sites and time of spawning
were determined, through planned surveys or various studies by the
collection of ripe fish in specific river reaches in different years
' and, for some species, by the collection of larval fishes downstream
from documented or suspected spawning sites.
' 3. Migrations Movements and Interchange between Stocks. Some
endangered Colorado River fishes are known to migrate to specific
spawning areas but return to a home area during the remainder of the
year. The Colorado squawfish migrates long distances to spawning
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