7989

• UCREFRP Catalog Number: 7989
• Author: Crowl, T. A. and N. W. Bouwes.
• Title: Modeling Population Dynamics of Colorado Squawfish, Razorback Sucker, and Humpback Chub
• USFW Year: 1997.
• USFW - Doc Type: for Management Objective Development.
• Copyright Material: NO

The basic model structure is:
N~,=Nt+R-M+1-E
for each river section where N=number of individuals of a given age, R is the
recruitment from the previous age class, M is the number of individuals that die for that
age class, / is immigration from the upstream section for the age class, and E is
emigration out of the section for that age class above carrying capacity.
1. The sequence begins with spawning adults (initial population) occurring at
designated spawning areas. The number of spawning adults is equal to the sum of all
adults for a!I sections below the spawning area within the subpopulation boundaries
(e.g., Middle Green, Lower Green and Colorado River for Colorado squawiish). After
spawning, the adults move downstream to the adult habitat reaches identified and
assess the number of fish already present relative to the carrying capacity for adults. If
the number of adults already present equals carrying capacity, then the adults continue
to the next adult habitat section. If the carrying capacity is not exceeded, then a
number remains so that the carrying capacity is equaled and the remaining adults
continue downstream. For each habitat segment that the adults have to move through
in moving downstream from the spawning bed, a proportion die based upon an adult
mortality rate for dispersal. This means that the further an adult has to move
downstream, the less likely it is to survive.
2. The adults in the spawning beds produce a number of eggs per female (set by a
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