9524

• UCREFRP Catalog Number: 9524
• Author: Kitcheyan, C. D. and e. al.
• Title: Evaluation of the Effects of Stage Fluctuations on Overwinter Survival and Movement of Young Colorado Pikeminnow in the Green River, Utah, 1999-2002.
• USFW Year: 2004.
• USFW - Doc Type: Denver.
• Copyright Material: NO

during the winter of 1996-1997 did not dismantle ice cover or promote formation of frazil ice
and ice jams. Whatever the cause, it is likely that ice jams form at several locations on the
middle Green River nursery area in most years.
As a result of stage changes, ice jams, and frazil ice formation, young fish redistribute to
more suitable habitats. Young Colorado pikeminnow prefer low-velocity backwater habitats,
and when these habitats are inundated, the fish abandon them and move to other low-velocity
habitats, sometimes to other backwaters several miles away and sometimes to low-velocity
micro-habitats within close proximity of the inundated backwater from which they re-inhabit
once the stage recedes.
When stage changes inundate nursery habitats and transform them into flow-through
environments, resident fish are flushed into the surrounding system and incur increased risk of
injury, predation, and metabolic costs associated with the search for another suitable nursery
area. Body weight and condition decline faster when fish activity is increased because energetic
reserves must be used to offset the cost of higher metabolic rate. The result may be higher
overwinter mortality.
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