Abstract

<jats:p> Allocation of energy by northern pike (Esox lucius) to maintenance, growth, and reproduction was estimated by a combination of laboratory and field techniques. Parameters were fitted to a bioenergetics model to determine the energy budgets of pike from Lac Ste Anne, Alberta. A poor fit was obtained when comparing the predicted ration and growth (from the model) to the estimated ration and growth (in the field), indicating that estimates for some budget components were in error. Further examination indicated that field ration data were probably inaccurate, and budgets were then calculated avoiding these data. The relative cost of maintenance was very low for age 0 fish (~60%) and increased with age. Relative allocations to reproduction and growth were similar from ages 1 to 3, although the relative energy allocated to growth declined from age 0 to 1. There were differences between energy budgets of males and females; females ingested 1.1- to 1.3-fold more energy annually than did males, and this extra energy was diverted into ovary growth, since total body growth was similar in the two sexes. There were also large differences in the seasonal timing of body and gonad growth between the sexes. Males increased in body energy over the summer and winter, while all testicular growth occurred in August. Females increased in body energy over summer only, while ovarian growth occurred mainly during the winter. Both sexes declined in energy stores over the spawning interval (March to May). </jats:p>