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Last modified
7/14/2009 5:02:36 PM
Creation date
5/24/2009 7:27:25 AM
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UCREFRP
UCREFRP Catalog Number
9544
Author
Collins, K., P. and D. K. Shiozawa.
Title
The Effects of Fish Predation on Backwater Invertebrate Communities of the Green River, Utah.
USFW Year
1994.
USFW - Doc Type
Provo, UT.
Copyright Material
NO
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measurable current except when there was wind blowing into them. Except for their <br />lack of vegetation they were very similar to the littoral region of a lake. Unlike the <br />main river channel of the Green River, backwaters seem to be quite productive. This <br />productivity probably attracts fish to the backwaters, which provides the opportunity to <br />test their effect on the invertebrate community. <br />Direct effects <br />The taxa which experience the greatest direct effects of fish predation appear to <br />be the chironomid genus Tanypus, the corixidae, and the planktonic adult copepoda <br />(including the predominant species Eucyclops s era u ). The corixidae and Tanypus <br />are both predators (the Tanypus may be omnivorous, see Merritt and Cummins 1984). <br />The predominant copepod genus, Eucyclops, is predominantly herbivorous (Wetzel <br />1983). All three groups were generally lower in the control areas and higher in the <br />perforated and closed areas where fish predation was diminished or absent. However <br />by week five there was a drop in adult copepod numbers which was less pronounced <br />in control areas than in the other treatments (Table 4). <br />It is possible that the elevated numbers of corixids in perforated and closed <br />treatments were a result of the insects crawling through the mesh in search of refuge <br />from predation or wind generated currents. We measured several anatomical <br />characters (including head capsule width) of corixids caught in perforated and closed <br />cages and found 76% of the individuals measured were first or second instars (which <br />are small enough to fit through the mesh). However, the few corixids caught in control <br />areas were all early instars as well. Whether increased densities of corixidae in caged <br />11
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