9384

• UCREFRP Catalog Number: 9384
• Author: Valdez, R. A. and R. J. Ryel.
• Title: Summary of Recovery Goals for the Four Endangered Fishes of the Colorado River Basin.
• USFW Year: 2000.
• USFW - Doc Type: Logan.
• Copyright Material: NO

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Humpback Chub - 3

c. a proportion of age 3 fish for each year that is not significantly higher than
30% or lower than 20% of the adult population for the same 5-year period
(Table 2).

Delisting Criteria

All Populations
1. All six known wild populations are maintained such that:
a. the estimated populations are not significantly less than the point estimates
ofthe first reliable estimate available (see Table 1) for each population for
8 years,
b. a trend in population point estimates for the same 8-year period that does
not decline significantly, and
c. a proportion of age 3 fish for each year that is not significantly higher than
30% or lower than 20% ofthe adult population for the same 5-year period
(Table 2).
2. Provide legal protection, assurances, and/or agreements for flows necessary to
recover the humpback chub.
3. Review and modify, if necessary, state and federal hazardous spills emergency
response plans to insure adequate protection from spills, including prevention and
quick response to spills.
4. Implement nonnative fish control in Yampa Canyon, Grand Canyon, and
Desolation/Gray Canyons, as needed, to recover the humpback chub.

Core Populations
1. Three core populations are determined to be genetically and demographically
viable and self-sustaining. Each of the core populations must have:
a. a minimum estimated population of 2,000 adults for a period of 8 years;
i.e., the lower 95% confidence interval of the estimated population of
adults exceeds 2,000.
b. a trend in population point estimates for the same 8-year period that does
not decline significantly, and
c. a proportion of age 3 fish for each year that is not significantly higher than
30% or lower than 20% of the adult population for the same 8-year period
(Table 2).