9432 ‎(2)‎

• UCREFRP Catalog Number: 9432
• Author: Modde, T. and M. Fuller.
• Title: Feasibility of Channel Catfish Reduction in the Lower Yampa River.
• USFW Year: 2002.
• USFW - Doc Type: Vernal.
• Copyright Material: NO

passageway and have moved up and entered the fish trap, they must be handled and
processed by researchers. Presently, a series of vertically positioned 2.1-cm
diameter aluminum conduits (0.9-cm spacing) comprise a baffle at the uppermost
end of the fish trap which prevents larger fish from continuing further upstream.
Larger fish upstream of the dam are prevented from moving downstream through the
fish passageway by a series of four, vertically- stacked trash grates (1.9-cm
spacing) and by a concrete bulkhead. Smaller bodied-fish (less than 100 mm total
length [TL]) are able to freely pass through the 0.9-cm spaces between the
conduits and trash grates and therefore can move uninhibited both up- and
downstream through the passageway. These smaller fish included native speckled
dace, and nonnative cyprinids, (fathead minnow, sand shiner, and red shiner), and
other juvenile native (bluehead, flannelmouth, and roundtail chub) and nonnative
fish (carp, green sunfish, white sucker, etc.) of the larger-sized forms.
The passageway could be converted to a "run-of-the-river" passageway, if
desired. This would require removing the aluminum baffle at the head end of the
fish trap and the stop-log panel located in a slot of the concrete head wall
immediately upstream of this baffle. Additionally, some of the vertical bars of
all the vertically-stacked trash grates that are upstream of the slide gate would
have to be removed to increase spacing for larger fish to pass through.
Alternatively, these trash grates could be removed altogether. The slide gate
would remain open (1-m wide) and along with the opening created by removal of the
stop log panel (0.5-m wide) adjacent to the slide gate would allow fish to pass
freely upstream. The new 0.5-m wide opening created by removing the stop log
panel would function similar to the orifices in the downstream aluminum baffles.
One of the major features of the fish passageway is the fish trapping
facility located at the upper end or forebay. Here, fish are dip-netted by hand
and placed in a 2.7-m wide by 2.7-m long collapsible net. An electrical, 2-ton
crane-hoist facilitates lifting the fish and net from the fish trap. Fish are
then dumped onto a sorting table where they are sorted, examined, counted by
species, and placed in one of two concrete holding tanks. An electric
submersible sump pump provides water to the holding tanks. Native fish and
salmonids exit one of the holding tanks through a 0.3-m underground PVC pipe and
enter the river approximately 30 m upstream of the dam; nonnative fish are
removed.
Studies of the Gunnison River
Several interdisciplinary studies conducted over the past decade as part
of the Aspinall Unit investigations have addressed the hydrology and
geomorphol ogy of the Col orado and Gunni son ri vers as wel 1 as the 1 i fe hi story and
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