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

implicated in the decline of the Colorado squawfish, the rarity of juveniles (70-400 mm
total length) suggests that the post-larval (<70 mm) squawfish that inhabit backwaters
may be experiencing high mortality rates (Karp and Tyus 1990). Since juvenile
squawfish are piscivorous they would likely benefit from high densities of non-native
minnows, but post-larval squawfish have a diet very similar to the red shiner which is
the most abundant backwater species. Our results, which indicate that backwater
fishes can significantly impact their resources, coupled with experimentally observed
spatial overlap, suggest that squawfish may be suffering from resource competition
during their post-larval stage (Karp and Tyus 1990). More research is necessary to
determine if this is the case.
In summary, we conclude that it is possible for fish in large river systems to
structure invertebrate communities, at least in selected habitats. The direct
consequences of fish predation can also have indirect effects on other invertebrate
groups through cascading trophic interactions. This depletion of food resources by the
fish community may have negative repercussions for native fish species such the
Colorado squawfiish.
14