Fish aggregations at fronts may be caused by either increased food ava
ilability or better thermal conditions at the front, but a quantitativ
e evaluation of the effects of fronts on fish has yet to be done. Bioe
nergetics models were used to evaluate the growth rate potential of a
cool-water fish, the chinook salmon (Oncorhynchus tshawytscha), and a
warm-water fish, the striped bass (Morone saxatilis), across thermal f
ronts of different temperatures and prey concentrations. The distribut
ions of growth rate potentials across these fronts depended on fish ph
ysiology, the temperatures encompassed by the front, and prey distribu
tions across the front. When food was distributed uniformly across the
front, the growth rates of both species were highest at their optimal
temperatures, if sufficient prey was available. Lower temperatures we
re better for growth if prey availability was low. Increased food avai
lability at the front enhanced fish growth rate potential at the front
. Actual growth rates depended on whether the fish behaviorally select
ed habitats by temperature, food, or growth rate potential. Results il
lustrate that prey patchiness and the nonlinearities inherent in the r
elationship of fish growth to temperature and prey availability must b
e considered in order to evaluate how a population of fish might respo
nd to a front and how the front might affect fish growth and productio
n.