8216

• UCREFRP Catalog Number: 8216
• Author: Crowl, T. A. and L. Lentsch.
• Title: Estimating Northern Pike Predation on Colorado Squawfish in the Middle Green River
• USFW Year: 1996.
• USFW - Doc Type: A Bioenergetics Approach.
• Copyright Material: NO

' Methods
Bioener~etics Model
' We estimated otential redation b northern ike on Colorado s uawfish b combining field data
P P Y P q Y
' on food habits, growth, thermal experience and energy expenditure associated with individual
movement estimates with a bioenergetics model (Hewett and Johnson 1992) parameterized for
northern pike growth and consumption (Bevelheimer et al. 1985, Wahl and Stein 1991). The
bioenergetics model is based on a mass balance equation:

' C,,,~ is maximum physiological consumption which varies as a function of predator body mass
and temperature. Pis the proportion of C,,,~ actually consumed, with values ranging from 0 to
' 1. Growth G was obtained from field measurements• metabolism M, which includes costs of
' standard metabolism, activity, and specific dynamic action (or heat increment, the energy used
to process a meal), changes as a function of body mass, temperature, and swimming speed;
i
and waste W which includes egestion and excretion losses, is modeled as a constant proportion
' of ration. The model is most commonly used to estimate the consumption rate (P*C,„~
required to satisfy observed growth, or, conversely, to estimate growth if consumption is
known. The energy density of prey (calories or joules per gram wet body mass) determines
' the quantit of re required to satisf a given growth rate: less prey of high energy density
Y P Y Y
' are required. Bioenergetics models developed to date have accurately predicted consumption
' 4