7326

• UCREFRP Catalog Number: 7326
• Author: McAda, C. W., K. Seethaler and R. S. Wydoski.
• Title: Progress Report June 1, 1974 - October 31, 1975 Investigations of the Movements and Ecological Requirements of the Colorado Squawfish and Humpback Sucker in the Yampa and Upper Green Rivers.
• USFW Year: 1975.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

. ~ lz
identifying larval fish in the field, representative samples were
preserved and returned to Logan for identification. Because of the
rigorous field schedule these fish have not yet been identified.
Juvenile bluehead and flannelmouth suckers were readily collected in
the Yampa and Green Rivers, but no juvenile humpback suckers were
collected.
Few investigators have collected juvenile humpback suckers even
though their keel is developed at two-three inches in length (Minckley,
personal communication), and the fish should be readily recognized as
humpbacks.
Acme and Growth
Problems have been encountered that make reliable age estimates
f
rather difficult. At this point, only adult humpback suckers r-ave
been collected. After maturity, growth of suckers~in general (Carlander
1969) slows greatly, scale annuli are laid down very close together and
in many cases worn off before the following year's annulus is 1-aid
down. Because these fish ?rP ~^Arp~ no effort ,.;ill b~ made to sacrifice
the fish to obtain other boney parts for ageing. Fish obtained during
the fall of 1974 have been tentatively aged at 5 to 7 years. Most likely
these fish are older than has been estimated.
_ Flannelmouth and bluehead suckers are also being studied for age.
and g-°owth information, but less difficulty should be encountered in
their case. All size classes have been collected and other boney parts
can be obtained for validation of the scale method.