9463

• UCREFRP Catalog Number: 9463
• Author: Badame, P. V. and J. M. Hudson.
• Title: Reintroduction and Monitoring of Hatchery-reared Bonytail in the Colorado and Green Rivers; 1996-2001.
• USFW Year: 2001.
• USFW - Doc Type: 03-13,
• Copyright Material: NO

growth and released the following April. In two of the six years of stocking, there were both
spring and fall release events which were comprised of multiple cohorts.

Monitoring Stocked Fish

A variety of methods were employed over the six years of monitoring in the Green and Colorado
rivers. Sampling efforts used specifically to monitor bonytail consisted of electrofishing, seining,
and hoop and fyke netting concentrated in an area 0 to 20 RM down stream of the release sites
with occasional sampling down to the confluence. Electrofishing was the only method employed
every year in both the Green and Colorado river reaches. Electrofishing consisted of a single boat
shocking one shoreline and habitats such as backwaters or flooded tributaries. Seines (6 mm
mesh, 4.5 m long x 1.2 m tall) were used to sample discrete habitats such as backwaters, flooded
tributaries, or small side channels. Multiple hauls were made in each habitat to adequately sample
it. Fyke and hoop nets of varied size were generally used to sample shoreline, eddy, and some
backwater or tributary mouths. The majority offyke and hoop nets used had 1 m hoop diameters,
12-25 mm mesh, and were 2 m long. On average, hoop nets were set for 24 hours and then
checked and moved. Trammel nets (23 m long, 1.2 m deep, 24 mm front panel mesh, 288 mm
interior panel mesh) were also tested in 1998 and again in 2000 with little success in capturing
small bonytail. The trammel nets were set for six hours in the evening and checked every two
hours. A wide variety of habitats were sampled with the trammel nets.

Additional projects conducted by the Utah Division of Wildlife Resources (UDWR) and other
state and federal agencies have also captured stocked bonytail. On the Green and Colorado
rivers, these projects included Interagency Standardized Monitoring Program (ISMP) sampling
for larval and adult pikeminnow (seining and electrofishing), nonnative cyprinid removal (seining),
and Colorado pikeminnow (Ptychochielus lucius, CPM) population estimates (electrofishing) on
the Green and Colorado rivers.

The lower Green River CPM population estimates provided the most intensive sampling to date.
The effort consisted of electrofishing both shorelines concurrently from the Green River release
site (RM 120) to the confluence with the Colorado River (RM 0), four times in March-May 2001
and three times in April-May 2002. This intensive monitoring and even longitudinal distribution
of effort aUowed for a more in depth evaluation of dispersal, overwinter survival, and habitat use
within the Green River. Unfortunately, the vast majority offish collected during this time were
marked with CWT's, which only reveals that a fish is a hatchery-reared bonytail. Information
such as stocking date, size at stocking, growth, and movement patterns could not be determined.

Analysis of recaptures

The process of comparing returns for various cohorts and stocking seasons is complicated by the
use of multiple recapture methods and widely varied stocking densities. To alleviate some of this
clutter, catch rates are defined in two ways. First, the standard catch per unit effort (CPUE) for

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