7971

• UCREFRP Catalog Number: 7971
• Author: Tyus, H. M.
• Title: Evidence for Homing in Colorado Squawfish,
• USFW Year: 1985
• Copyright Material: NO

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Evidence for homing in Colorado squawfish,
Ptychocheilus Lucius
H. M. Tyus
U. S. Fish and Wildlife Service
447 E. Main St., Vernal, Utah 84078
Nestract--Spawning migration of 23 radiotelemetered Colorado
squawfish to two sites in the Yampa and Green rivers, 1981-1983
` suggested homing behavior. Movement patterns of these fish displayed
similarities to migrating salmonids, indicating olfaction as a
I possible mechanism used in navigation. Recaptures of Colorado
squawfish indicated a year-to-year fidelity to the spawning grounds.
Colorado squawfish were reported in many early accounts (Sigler
and Miller 1963) and documentary proof was obtained by Fish and
Wildlife Service workers in 1981 (Tyus et al. 1981). Since that
time two spawning areas have been identified in the Green River Basin
of Colorado and Utah, and Colorado squawfish have been radiotracked
round trip distances of 400 km in their travel to them (Miller
et al. 1983, Wick et al. 1983). Movement patterns obtained from these
fish display both upstream and downstream potamodromous migrations
(Myers, 1949) and suggest a homing ability for which no mechanism
has been identified. This paper presents evidence for the develop-
ment of a homing hypothesis based on the results of Fish and Wildlife
Service studies in the Green River Basin of Colorado and Utah, 1980-
1983. This evidence is contrasted with hypotheses developed by others
for salmon and other fish species.
METHODS
Colorado squawfish were collected primarily by electrofishing
but some were also collected by seining and trammel netting.
Collections were made early in the year so fish might have time to
recover from surgery before the mid-summer spawning season, and to
reduce the risk of secondary infection.
After their capture, the Colorado squawfish were placed into
a 200 mg/L solution of tricaine methylsulfonate. When the fish were
anesthesized, they were surgically implanted with radiotransmitter
modules using a procedure similar to that of Bidgood (1980). Sutures