9435

• UCREFRP Catalog Number: 9435
• Author: Haines, B. and T. Modde.
• Title: Humpback Chub Monitoring in Yampa Canyon, 1998-2000.
• USFW Year: 2002.
• USFW - Doc Type: Project Number 22a4,
• Copyright Material: NO

fish 70-130 mm and age 2 fish 130-190 mm TL for both humpback and roundtail chubs. These

size classes are consistent with otolith aged Yampa River Gila (Steve Ross, University Southem

Mississippi, personal communication) and with length-frequency aged Gila from Westwater

Canyon (Chart and Lentsch 1999).

Gear efficiency. Catch rates of humpback chub differed greatly depending on the gear

used (Table 4). Electrofishing rafts were the most effective, capturing 80% of the total fish at a

rate of 0.8 fish per h. The most effective method consisted of two electrofishing rafts with a

crew of two on each raft and a support crew of four or five additional people in following rafts.

The most effective electro fishing results were the last two passes in 2000 when 18 and 17 fish

were caught. Angling captured nine humpback chub at a rate of 0.04 fish per h. Usually we had

six to eight anglers on a trip. Often angling was done in shoreline areas with boulders and eddies

and fast main channel flow where electrofishing was not effective. Seining worked well for

capturing juvenile Gila. Humpback chub juveniles were captured at a rate of 0.15 fish per seine

haul. Hoop nets failed to catch any humpback chub, although a few roundtail chub and channel

catfish were captured.

Adult population estimates. Although the capture-recapture data did not yield enough

recaptures for a satisfactory population estimate (Table 3), we can examine the data to get some

idea of population size and how to design a study that will give a satisfactory estimate. We used

the 2000 data in program CAPTURE for all model estimators and tabulated for each model the

selection criterion score, population estimate, standard error, 95% confidence limits, and the

10