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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factors (Figure 1). Some life stages were combined because (a) they have similaz habitat
requirements and limiting factors (e.g., juveniles and adults), (b) their life history requirements
and controlling factors aze poorly understood (e.g., age-0, age-1 fish in winter habitat), or
(c) they aze hypothesized to have weak effects on recruitment dynamics (e.g., juveniles).
' Model Results
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The life-history model illustrates how recruitment and outcomes of management actions
are potentially affected by multiple and interacting biotic and abiotic processes at different
temporal scales. For example, number of age-0 Colorado squawfish that survive to fall may be a
function of the number of larvae produced, their growth rates, predator density, and quantity and
quality of backwaters available that summer. Predation, habitat selection, and stochastic events
are factors that affect survival and growth on a daily basis. The model also conveys an annual
temporal structure that begins with deposition of embryos in the substrate. Recognition of
various temporal scales is important because it emphasizes that recruitment to a life stage is a
function of numerous processes occurring at different times and that in order to explain
chazacteristics of a population it might be necessary to study events that occurred days, months,
yeazs, or even decades ago. Similazly, this temporal aspect of Colorado squawfish life history
should be considered when management actions aze implemented, because detectable changes in
population structure may not occur until well into the future.
Four of five compartments in the life-history model refer to age-0 fish. This structure
was not intended to imply that eazly life stages aze more important than juveniles or adults;
rather, it is due to the dramatic changes in physical ability and environmental requirements that
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