8114

• UCREFRP Catalog Number: 8114
• Author: Nesler, T. P.
• Title: Five-year Stocking Plan for Endangered Colorado River Fish Species in Colorado.
• USFW Year: 1998.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

this pattern is for razorback sucker in the Colorado River below Palisade. For razorback
sucker and bonytail, the two fish sizes represent the estimated size of fish after the first and
second growing seasons. Based on monitoring results after replication of each combination
in each river, production may be modified in the third year to focus on the apparent optimal
fish size and season to stock in each river. This approach is consistent with draft
recommendations made by Burdick and Bonar (1997) for stocking razorback sucker. For
razorback sucker and bonytail, PIT tagging is not considered feasible due to cost, or
necessary due to the absence of riverine populations in Colorado. A less-expensive batch
mark for distinguishing between cohorts stocked each year would be useful for tracking year-
class composition and sUIVival of stocked fish in the adult population over time. For
Colorado pike minnow , the two sizes represent the first and subsequent sizes at which the fish
may be PIT tagged prior to stocking. Due to the presence of a wild population of Colorado
pikeminnow in the adjacent downstream reach, it is recommended that PIT tagging be used
on all Colorado pikeminnow stocked. The cost for this PIT tagging will range from $3,000
to $9,000 per year based on 800-2,400 fish and $3.75/tag. Monitoring would require the
implementation of population estimate protocols (see Osmundson and Burnham 1996) for
adult fish in each river reach. This approach is considered preferable to ISMP (Interagency
Standardized Monitoring Program) adult catch/effort index until a relationship between the
two parameters can be established. It is also possible for mark-recapture population
estimates to be derived from PIT tag data collected using ISMP sampling protocols conducted
on any of the target reaches. This would add at least four additional monitoring reaches to
ISMP.

The target objective of stocking for each of the three species is to meet the
abundance/biomass based criterion with the presence of three adult age groups sUIViving in
each river reach. For razorback sucker, these age groups are 5-7; for bonytail, age groups
4-6; and for Colorado pikeminnow, age groups 6-8. The cumulative sUIVivallabundance/
biomass of these age groups is desired to achieve the population objective in the river.
Using monitoring to evaluate sUIVivaI and abundance post-stocking, subsequent numbers of
fish stocked may have to be increased or decreased. The presence of an adult, multi-year-
class population in the target river reaches is desired to further detennine spawning and
reproductive success, and the effects of limiting environmental factors that may be
influential. The persistence of a potentially long-lived, stocked adult population would thus
contribute to recovery of subsequent self-sustaining wild populations of these species in these
river reaches.

Stocking of humpback chub in Colorado is not anticipated at this time. This species
is characteristically associated with canyon-bound river habitat, which dictates where stocking
would occur. Within the two canyon reaches known to support humpback chub in Colorado,
Yampa Canyon on the Yampa River and Black Rocks on the Colorado River, research has
failed to discover a significant threat of extirpation to either population under current
environmental conditions. This includes the presence of an abundant and potentially
predatory channel catfish population in both reaches. The Black Rocks population has
demonstrated a relative stability since monitoring began in the early 1980s (see . Miller et aI.

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