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

Imprinting

It is presumed that Colorado squawfish and razorback sucker return to natal
areas by use of olfactory cues (i.e., memory of specific home-site odor
bouquet). If the young fish are imprinted, it must occur at an early
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 when imprinting occurs (i.e., egg stage, swim-up, or as the
young fish 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, then maintenance of release sites
would be necessary 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 HSOB, 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
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.

Methods: Place traps in hatchery discharge pipes and attempt to attract
fish that were reared at Ouray ~nd released into the Green River 3 to 5 years
previously.

H4: Colorado squawfish and razorback sucker can be artificially-imprinted to a
suitable synthetic substance.

Task: Test synthetic substances for imprinting effectiveness.

Methods: Obtain newly-fertilized eggs from a hatchery, mark them during
incubation and early larval development, rear to sub-adult size, and release
at a re-introduction site. Three groups would be marked: morpholine, phenethyl
alcohol and a control group that would be hatched in hatchery water. The
reintroduction site would be carefully chosen for its adequacy as a future
spawning and rearing area, and the fish would be attracted as spawning adults

15