7872

• UCREFRP Catalog Number: 7872
• Author: Bestgen, K. R., et al.
• Title: Recruitment Models For Colorado Squawfish
• USFW Year: 1997.
• USFW - Doc Type: Tools For Evaluating Relative Importance Of Natural And Managed Processes - Final Report.
• Copyright Material: NO

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of a simulation, data that described the numbers, size distribution, and growth rate distributions
of survivors and mortalities were output for further analysis.
Simulation Results
We implemented the IBM under several different sets of conditions to evaluate the
relative effects of red shiner predation on survival and TL of squawfish cohorts at the end of the
growing season, as a function of thermal regime, arrival time, larval growth rate, and predator
density. For most simulations we assumed conditions of turbid water with alternate prey present,
because we expected these conditions to be fairly typical for backwater nursery habitats. Unless
specified otherwise, we used a moderate mean baseline growth rate of 0.3 mm/d for the larvae,
and a moderate red shiner density of 3 predators/mZ. Results reported below each represent the
mean of three replicate simulations started with different random number seeds.
An additional simulation was added in the final stages of report preparation at the request
of a funding sponsor (E. Wick). This simulation compared survival and growth of a cohort of
Colorado squawfish in the middle and lower Green River where water temperatures, arrival date
of Colorado squawfish larvae, and timing of availability of alternative prey may differ. These
results are reported in Appendix I.
Effects of Thermal Regime and Colonization Date
To examine the effects of thermal regime and the timing of backwater colonization

(arrival) by larvae, we simulated six scenarios using warm and cool temperatures with early,
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