9299

• UCREFRP Catalog Number: 9299
• Author: Anderson, R. and J. Mumma.
• Title: Aspinall Studies
• USFW Year: 1999.
• USFW - Doc Type: Annual assessment of Colorado Pikeminnow Larval Production in the Gunnison and Colorado Rivers, Colorado 1992-1996.
• Copyright Material: NO

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· The intermediate flow year (1996) was the year for highest Colorado pikeminnow
YOY and NNC densities in summer and fall backwater habitats in Moab, but and was
also the year with the least NNC and Colorado pikeminnow drift densities in Loma.

· If there had been intermediate densities for Colorado pikeminnow and NNC in 1996,
there would have been strong correlations between flow and fish densities in the drift
and in backwaters.

· Flow generally integrates and is correlated to several physical variables that could
influence larval Colorado pikeminnow production such as water temperature, sediment
load, larval drift rates, spawning and nursery habitat availability, substrate flushing,
siltation on cobble spawning bars, and aspects of water quality.

· Non related flow variables that could influence Colorado pikeminnow production
independently of flow include: number of spawning adults per year, variation in
locations of spawning sites, physiological condition of spawning adults, larval food
availability, number of predators, and unpredictable water quality factors (pollution,
mud slides, spills, etc.).

· Results of this five-year study (1992 to 1996) indicated a strong relationship between
flows and larval pikeminnow production. However a different five-year period may
not have produced similar results. A longer sampling period appears to be necessary
to help explain seemingly anomalous years like 1992 and 1996 and the effect of,
multiple years.

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