8271

• UCREFRP Catalog Number: 8271
• Author: Tyus, H. M., J. H. Williamson and P. B. Johnsen.
• Title: Chemoreception, Imprinting, and Propagation of Colorado Squawfish and Razorback Sucker.
• USFW Year: 1990.
• USFW - Doc Type: Denver, Colorado\
• Copyright Material: NO

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 s awning grounds are genetically different. C/ ~ Z
~~ - _ __.
Methods: Obtain tissues from both groups, evaluate genetic differences as
above. ~ ~
H`~ 4~~
Imprinting
~~ ~- z--
It is presumed that Colorado squawfish and razorback sucker return to natal -~~zs ~~
areas by use of olfactory cues (i.e., memory of specific home-site odor w,4i~
bouquet). If the young fish are imprinted, it must occur at an early i~--~
ontogenetic stage as in pink salmon and other fishes which emigrate
immediately after emergence (Hasler and Scholz 1983). Although it is of
interest to know if imprinting occurs in the egg, at swim-up, or as they
migrate downstream from spawning areas, some problems can be avoided if the
fish can be imprinted to a synthetic chemical.
If artificial imprinting is successful, maintenance of spawning populations
1\~~,~.j•"`~ thus established would require operation and maintenance of release sites to
= provide release of the imprinting chemical in perpetuity. Therefore, it would
also be important to learn if reproductive by-products in spawning areas could
function to attract young in the absence of imprinting odors.
H3: Colorado squawfish and razorback sucker are imprinted to a specific home-
site odor bouquet (HSOB) on spawning areas, and use this induced memory to
return to those areas as spawning adults.
Task: Determine if fish learn a HSO6, subsequently use these as a cue to
locate spawning sites.
Methods: Capture local spawners from two areas, fertilize eggs from those
sites, split egg lots into two from each area and place one-half of each lot
in baskets of media and return to parental spawning sites. After 1-2 weeks
remove these to hatchery, rear them to about 300 mm (about 1 year before the
males are expected to mature) and mark them with coded wire or PIT tags. Of
these, stock all but 100 fish in areas upstream and downstream of the hatching
sites. Of the remainder, radiotag 50 fish from each location and release them
upstream (25) and 'downstream (25) of spawning areas in the summer or fall
j after they first reach sexual maturity. Monitor these fish and determine their
'~, behavior during the next spawning season.
Task: Determine if razorback suckers reared at the Ouray hatchery facility
are imprinted to hatchery discharge water. _
7