9544

• 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

INTRODUCTION
The role of biotic interactions in structuring natural communities has been well
studied (Connell 1983, Schoener 1983, Sih et at. 1985). Investigations of freshwater
lentic habitats, especially pelagic, have revealed that predator induced trophic
cascades are often a driving force in the communities (Carpenter et at. 1987,
Johannes et at. 1989, McQueen et at. 1989, McQueen 1990, Shapiro and Wright
1984). However, studies of freshwater lotic communities have had mixed results. Lotic
communities with coarse substrates have failed to show significant invertebrate density
effects from vertebrate predation (Allan 1982, Reice 1983, Flecker and Allan 1984,
Culp 1986, Reice and Edwards 1986), while invertebrates in pools and soft substrates
of small streams have responded to fish predation (Wilzbach et at. 1986, Schlosser
and Ebel 1989, Angermeier 1985, Gilliam et at. 1989). However, few investigations
have tested predatory effects of fishes on invertebrate communities of large rivers. In
this study we examined the role of fish predation on the structure of invertebrate
communities of the Green River, a large river in eastern Utah.
Backwaters are defined as shallow ephemeral embayments adjacent to the main
river channel with no measurable water velocity (Tyus and Haines 1991). At least
eight native, and fifteen non-native fish species occupy backwaters of the Green River
from mid-summer through fall (Haines and Tyus 1990). One of the native fish species,
the Colorado squawfish (Ptychocheilus lucius), uses the backwaters as a nursery area
(Haines and Tyus 1990). The most abundant backwater fish species are (in
descending order) red shiner (Cyprinella lu n i , fathead minnow (Pimephales
3