7742

• UCREFRP Catalog Number: 7742
• Author: Gilpin, M.
• Title: A Population Viability Analysis of the Colorado Squawfish in the Upper Colorado River Basin
• USFW Year: 1993.
• USFW - Doc Type: A Report to the United States Fish and Wildlife Service, Denver, Colorado.
• Copyright Material: NO

Squawfish Population Viability Analysis --July 1993

Page 9

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Figure 1.2

Age

Future reproductive output ceases to be worth as much, as it must be
discounted by a higher adult mortality rate. This higher rate is the sum of
natural mortality plus human harvest mortality. This has the effect of
changing the optimal life history. Probably, a fish is "better off' by
reproducing earlier and with greater effort, even if this effort slows
growth and places physiological stress on the organism that shows up as
even further increases in adult mortality. But such an evolutionary
adjustment takes very long periods of time, especially with an organism
with as long a generation time as the squawfish. Doubtless, the life history
and consequent demography of the Colorado Squawfish must be considered
out of equilibrium with its current ecological situation. That is, the
demographic rates that prevail today must largely reflect the evolutionary
compromises attained by the species before modern man entered the
Colorado River Basin.

1.8 Data for a Demographic Analysis.

The central database utilized for life history analysis was the 1400 record
CRFP database that covers the years from 1978 to 1989 (obtained from
Chuck McAda at the USFWS field station in Grand Junction, Colorado).
Other sources of data could shade provisional judgments drawn from these
data. The CRFP database is not everything that one would like, but it is