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 28

Figure A.2 Representation of the possible pattern of migration in the Colorado
squawfish.

Slatkin repeated his simulation using a one dimensional stepping-stone model and
achieved significantly higher values of p(l). Thus we might expect the correlation
for the Colorado squawfish to lie somewhere slightly above the one shown in
figure 1. This means that if a p(l) value of greater than 0.07 was obtained it would
not be possible to say whether there was a risk of inbreeding or not, however if the
value was less than 0.07 the risk could be dismissed.

3.1 Introduction to Density Regulation

Density dependent growth regulation seems to be used less in population
viability analysis than in other areas of applied ecology, for example, in
optimal harvesting theory. One possible reason for this is that species
treated under endangered species law are thought to be well below their
natural carrying capacity and thus below the density at which negative
feedback would operate to slow population growth. For example, almost
all of the analysis done on grizzly bears and the desert tortoise is based on
demographic analyses that do not adjust parameters for changes in
population density. On the other hand, the fisheries literature is rich in
mathematical models that account explicitly for density levels, commonly
referred to as stock levels. The analysis to follow approaches the question
of density dependence in squawfish viability through various lines of
inference. It must be stated at the outset, however, that actually fitting