7978

• UCREFRP Catalog Number: 7978
• Author: Tyus, H. M.
• Title: Chemoreception, Imprinting, and Propagation of Colorado Squawfish and Razorback Sucker
• USFW Year: 1992
• USFW - Doc Type: a Plan of Study
• Copyright Material: YES

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areas, staff experience with propagation of the fish, and reduced costs
associated with using an existing facility. Release of imprinted fish into
the Green River would ostensibly provide the best existing habitat to insure
high returns. However, the importance of this work dictates that more than one
~ite be used if possible, and results compared. This study is restricted to
the Upper Colorado River Basin, and it is noted that state regulations may not
allow work on the endangered fishes outside the basin.

WORK ITEMS:

Genetic Assessment

Recent studies indicate that some Colorado squawfish and razorback suckers
in the Green and Yampa rivers return to the same spawning sites for spawning
(Wick et al 1983, 1986; Tyus 1985, In press; Tyus and Karp 1990). If return to
these specific spawning sites is a general reproductive phenomenon for these
species (i.e., the fish return to natal spawning areas as adults and spawn in
the reach(a) or exact site(b) at which they were hatched), then genetic
differentiation among disjunct spawning populations or stocks is suspected.
The existence of genetically-distinct populations of Colorado squawfish and
razorback suckers should be evaluated for these different spawning areas could
be evaluated by collecting and analyzing genetics data. In addition, there may
be a genetic basis for sub-stocks within a spawning area; in squawfish, the
different rheotaxes (positive and negative) noted in migrating fish suggest
the existence of these sub-stocks. These different movement patterns must also
be considered in testing the following hypotheses:

H1:Breeding populations of Colorado squawfish and razorback suckers differ
genetically.

Tasks: Determine if Colorado squawfish and razorback sucker are
reproductively isolated between (a) reaches or (b) spawning sites:

Methods: Identify spawning sites in the upper Colorado River Basin. At each
site during the spawning season, capture fish in breeding condition and mark
them with a uniquely-numbered tag. Take superficial somatic tissues and
gametes from each fish for genetic analyses. If possible, obtain tissues and
sex products of fish known to use reaches(a) and sites(b) for spawning, or of
fish emerging from such ar.eas. Perform analyses (i.e. allozymes and mtDNA) to
determine differentiation within and among breeding populations. In addition,
emerging larvae should be taken from each spawning site and these fishes also
subjected to genetic analyses. Use fish from Green, Yampa, and Colorado
rivers, and use northern squawfish as the outgroup.

H2:Upstream and downstream migration (i.e. positive and negative rheotaxis) in
Colorado squawfish is under genetic control.

Task: Determine if Colorado squawfish that migrate upstream and downstream
to reach the same spawning grounds are genetically different.

Methods: Obtain tissues from both groups, evaluate genetic differences as
above.

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