Kj. Hartman et Sb. Brandt, SYSTEMATIC SOURCES OF BIAS IN A BIOENERGETICS MODEL - EXAMPLES FOR AGE-0 STRIPED BASS, Transactions of the American Fisheries Society, 122(5), 1993, pp. 912-926
Laboratory experiments were conducted to measure prey consumption and
metabolism of age-0 striped bass Morone saxatilis for a bioenergetics
model for this species. In many bioenergetics models, resting metaboli
sm is multiplied by a factor of one to two to account for energy expen
ded in active metabolism. We estimated this activity multiplier (ACT)
indirectly from laboratory experiments and found it to average 2.47. W
e validated the bioenergetics model in the laboratory and found estima
tes of growth and consumption to be within 6.1% of measured values at
20-degrees-C, but growth was underestimated and consumption overestima
ted by as much as 33% at 6.9-degrees-C. The bioenergetics model was us
ed to evaluate the influence of parameter uncertainty upon model resul
ts. In general, parameters with the greatest uncertainty (largest 95%
confidence interval relative to the mean) tended to be least sensitive
to errors, whereas those measured with greater precision were more se
nsitive. Changing the value of ACT from the mean to the 95% confidence
limits had little effect on consumption estimates, but uncertainty in
ACT could mean a 1.3-degrees-C range in the uncertainty of the upper
temperature that supports positive growth. If prey type and prey densi
ty influence parameter estimates, confidence limits of model parameter
s may be larger than the levels of variation normally used in model er
ror analyses. Estimates of maximum consumption (C(max)) for striped ba
ss fed live age-0 spot Leiostomus xanthurus, live polychaetes Nereis s
pp., or thawed bay anchovies Anchoa mitchilli were not significantly d
ifferent; however, when we used mean values to estimate the intercepts
for C(max) functions derived from the different prey types, the estim
ates did differ. Predator density had a positive effect on C(max) of a
ge-0 striped bass. Fish at densities greater than four per tank (0.85
m3 volume) had significantly higher maximum consumption rates than one
or two fish per tank. We conclude that bioenergetics modelers must pa
y particular attention to the methods used to generate data for model
development and attempt to match methods to the particular application
of the model.