7229

• UCREFRP Catalog Number: 7229
• Author: Kaeding, L. R. and M. A. Zimmerman
• Title: Life History and Ecology of the Humpback Chub in the Little Colorado and Colorado Rivers of the Grand Canyon
• USFW Year: 1983
• USFW - Doc Type: Transactions of the American Fisheries Society
• Copyright Material: YES

BIOLOGY OF HUMPBACK CHUBS IN THE GRAND CANYON
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FIGURE 6.-Diagra~m~matic representation of the study area, shoruing points of initial capture and subsequent recapture
of tagged huvnpback chubs. Numbers designate multiple observations.
2 and 3, were within 0.3 km of the release site;
the remaining 19 fish recaptured were displaced
an average of 3.8 km. No relationship was ev-
ident between time at large and displacement
distance.
Tagging can induce stress and latent debili-
tation in fish due to handling, secondary infec-
tion, and the drag effect of the tag-problems
that could result in downstream movement that
would otherwise not occur. Although many
humpback chubs were recaptured near their
original tagging site, which suggests that the
effect of tagging was not important, two fish
were recaptured in poor condition 2-4 km
downstream 1 or 2 days after release during the
1981 spawning season (Fig. 6). Fish experienc-
ingadverse tagging effects seem unlikely to make
significant upstream movements, however. Nine
of 10 tagged humpback chubs that moved more
than 0.3 km upstream had been tagged during
the 1980 or 1981 spawning period (April-June).
Seven were recaptured from the Little Colo-
rado during that same or the next spawning
season, whereas two were recovered from the
Colorado upstream from the confluence after
the spawning season. These recoveries suggest
that movement of adult humpback chubs within
the study area might be related largely to
spawning, and that this movement might occur
between rivers.
Analyses of Catch Statistics
Age-0 and Juvenile Fish
Minnow traps collected mostly age-0 hump-
back chubs, 80 ± 23 mm long (mean ± SD),
whereas seines collected age-0 and juvenile fish
92 ± 46 mm long. Mean C/f by seine was higher
during darkness than during daylight, except
during three sampling trips (August and Oc-
tober 1981) when waters were turbid in the
Little Colorado and at the confluence, and one
Quly 1980) when the water was clear in the
Little Colorado but small humpback chubs might
have been particularly abundant (Fig. 7). Al-
though it may be speculated that humpback
chubs eluded seines during daylight, water clar-
ity in the Little Colorado and the Colorado
readily allowed us to see that the number offish
escaping seines was trivial. Our data suggest that