K. R. Bestgen, K. A. Zelasko, and G. C. White. Monitoring ...

a side channel, and that a side channel is a main feature of the middle Green River spawning
area, Razorback Bar. Such areas should be considered for monitoring with passive PIT tag
detector antennae, which may substantially boost numbers of recaptured fish in each area.
The importance of tributary habitat in downstream and upstream reaches (nearly 35 and
40% use, respectively) of the lower Green River is notable, because those habitat types are
mostly unavailable in seasons other than spring when those places are inundated with snowmelt
runoff flows. Investigators should target such habitats to increase capture rates of razorback
suckers, especially in the upper reach of the lower Green River where more fish occur, both with
active sampling gear, and perhaps, with passive gear such as hoop nets, which may be deployed
and checked less frequently. Hoop nets deployed in low-velocity channel margin areas were an
effective gear to sample razorback suckers in the middle Green River from 1996–1999, and
captures made with those gears greatly supplemented fish captures compared to those made with
just electrofishing, which occurred mainly over Razorback Bar (Bestgen et al. 2002). Such
locations should also be evaluated for use of PIT tag detector antennae. In spite of their high
initial cost, high potential detection rates of fish in concentration areas such as flooded tributary
mouths may warrant their use, and in the longer-term, be cost effective compared to exclusive
use of active sampling gear. Flooded tributaries are also typically low-velocity environments,
which may be advantageous when deploying detection gear compared to the swifter flowing
main or side channels.
In the Desolation-Gray Canyon reach, razorback sucker capture numbers were relatively
low and were more uniformly distributed. The most upstream 10-mile section, which was just
downstream of the Sand Wash boat ramp and the main access for stocking hatchery fish, was
where the most fish were captured, but lack of concentration areas precluded more detailed
mapping of such. Fish macrohabitat use in that area was dominated by main channel captures,
with a smaller number of backwater and very few tributary (mainly Price River mouth) captures
(Figure 7). That area is sampled mostly earlier in the year during Colorado pikeminnow
abundance estimation (Table 5), so the importance of tributary habitat may be lower in that lower
flow period.
In the middle Green River, razorback sucker captures were also relatively uniform and
low relative to the lower Green River. Also similar to the Desolation-Gray Canyon reach, most
fish were captured in the two most upstream reaches and just downstream of the Split Mountain
Boat Ramp where most fish were stocked. We plotted the fine-scale distribution of razorback
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