7798

• UCREFRP Catalog Number: 7798
• Author: Richardson, S.
• Title: Conceptual Management Plan for Razorback Sucker Habitat Enhancement in Flooded Bottomlands, Escalante Ranch, Jensen, Utah.
• USFW Year: 1994.
• USFW - Doc Type: \
• Copyright Material: NO

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The rivers of the Upper Colorado River Basin are turbid and
contain large expanses of sand substrate. Production of
phytoplankton and zooplankton that form the basis for a food
pyramid are extremely low in the these rivers (Grabowski and
Hiebert 1989; Cooper and Severn 1994 a, b, c, and d; Mabey and
Schiozawa 1993). High turbidity obstructs the penetration of
sunlight that is needed for phytoplankton production. Backwaters
and embayments along the main river channels and flooded
bottom lands in off-channel areas provide favorable conditions for
phytoplankton production. Sediments deposited in these areas
where the water velocity is decreased provide nutrients and
sunlight penetrates the clearer water that allows phytoplankton
to flourish as primary producers and to stimulate production of
the food chain. Low velocity off-channel habitats become warmer
than the riverine environment in the upper basin (Kaeding and
Osmundson 1988; Osmundson and Kaeding 1989). The combination of
nutrients, sunlight penetration of the water column, and warmer
water temperatures in low velocity habitats provide the best
conditions for phytoplankton production in the upper basin.

B. Importance of Low Velocity Habitats to Zooplankton
Production. The importance of low velocity habitats to the
production of zooplankton for fish in riverine environments has
not been documented very well. Most riverine studies have
concentrated on macro invertebrates occurring in the drift (Waters
1969). Mabey and Schiozawa (1993) reported that the most
comprehensive studies have been made of the plankton communities
in the Orinoco River, Venezuela. Mean densities of cladocerans
and copepods (the most abundant taxa) were 421 organisms per
liter in the Laguna la Orsinera. Welcomme (1989) summarized
zooplankton densities in floodplains in a range of 270 to 10,000
organisms per liter. Mabey and Shiozawa (1993) documented
zooplankton densities in the middle Green River as 0.3 to 1.3
organisms per liter, 1.5 to 7.1 in the Ouray backwater, 63.4 at
Intersection Wash (another backwater), and 206 to 690 in Old
Charlie Wash (Woods Bottom) on the Ouray National wildlife
Refuge, located downstream from Vernal, Utah. Grabowski and
Hiebert (1989) reported 0 to 20 planktonic crustaceans
(cladocerans and copepods) per liter in the middle Green River
channel and 0.02 to 17 organisms per liter in backwaters during
1987 and 1988. In an open water habitat of the Moab Slough,
immediately upstream on the Colorado River from Moab, Utah, the
density of planktonic crustaceans (cladocerans and copepods)
averaged about 36 organisms per liter during the summer of 1993
(Cooper and Severn 1994a). Cooper and Severn reported a mean of 2
organisms per liter for backwater sites and a mean of 36
organisms per liter for open water wetlands. Samples of
planktonic crustaceans (cladocerans and copepods) from the
Escalante Ranch site on the middle Green River, upstream from
Jensen, Utah, contained 0 organisms per liter for the main
channel, a mean of 41 organisms per liter for backwater?, and a
mean of 71 organisms per liter for an open water wetland (Cooper