9466

• UCREFRP Catalog Number: 9466
• Author: McAda, C. W.
• Title: Population Size and Structure of Humpback Chub in Black Rocks, 1998-2000.
• USFW Year: 2002.
• USFW - Doc Type: Grand Junction.
• Copyright Material: NO

last sampling trip of 1999 when an experienced observer was available to sex the fish. The
sex ratio was not significantly different from 1:1.
Population estimates were highly variable depending on the model selected to make the
estimate. For example, estimates in 1999 ranged from 635 using Jackknife M,, to 1,118 using
Chao M,,. Model Mo was selected as the best estimator. Using the best model, population
estimates for adult humpback chub in Black Rocks were 764 (95% confidence interval,
512-1,206) in 1998, 921 "(723-1,208) in 1999, and 539 (223-1,497) in 2000. Mean for the
three years was 741.
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