9458

• UCREFRP Catalog Number: 9458
• Author: National Park Service.
• Title: Workshop on Population Estimates for Colorado Pikeminnow and Humpback Chub.
• USFW Year: 2001.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

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Predicting change in adult abundance

Estimates of annual population increase or decrease of adult Colorado pikeminnow in the Colorado
River based on expected recruitment and survival. Example is for 1998 (year at time I). Adults are
considered fish> 500 mm. Survival rate assumes 86%. Fish 474-499 mm are those expected to recruit
in following year (grow to at least 500 mm), based on an average growth increment of 25.8 mm for fish
of this size (see Osmundson 2001).
Fish 474-499 mm
Pop est percent number Adult Survival to Adults change
pop est yr i + 1 at yr i + 1 expected
1998
upper reach 435 1.4 6 412
lower reach 330 5.8 19 106
Whole river total 25 518 445 470 -9.3%