8133

• UCREFRP Catalog Number: 8133
• Author: Collins, K. and D. K. Shiozawa.
• Title: The Effects of Fish Predation on Backwater Invertebrate Communities of the Green River, Utah\
• USFW Year: 1996.
• Copyright Material: NO

treatments (weeks 1, 3, and 5) for those taxa which had significant p-values (a = 0.05) in
weighted ANOVA tests. Means for plankton densities were calculated on log(x+1)
transformed count data and then converted back into actual densities because of small sample
size and a negative binomial distribution (Elliot 1977).
RESULTS
Benthos
Nematode and the naupliar stages of copepods were the most abundant groups in the
benthos (Table 1). The densities of the major benthic taxa are within the range of previously
reported densities except for microcrustaceans (Mabey 1993, Wolz and Shiozawa 1995). Both
benthic copepods and cladocerans were found at higher densities than during a previous study
(Mabey 1993), and were more comparable to densities reported in that study for seasonally
inundated wetland areas near the river. At least four species of cyclopoid copepods were
present in the backwater benthos: EucyclQps s era , Euc c s nrionophorus,
Acanthocvclops vernalis, and Diacyclons bicus in datus, although A. vernalis and D.
bicuspidatus are in low numbers. At least 10 chironomid genera were collected in the benthos
over the period of our study: Chironomus, Glvptotendipes, CrDtochironomus, Polxpedilum,
Stempellinella. Nimbocera, Tan rsus, Lenziella, Tanypus, and Procladius. Only
Chironomus and Taus were abundant. We found two species of cladocerans present in the
benthos during our study: Ilvocaptus so di , and Macrothrix laticornis (Table 1).
Densities of naupliar and copepodite copepods were significantly lower (a = 0.05) in
the closed treatments than in control areas (Table 2), while the chironomid genus Tan us was
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