Energy budgets, based on laboratory and field studies in 1967 and 1968, were constructed for young-of-the-year white bass Morone chrysops. Major food items in the diet of the fish were cladocerans, copepods, amphipods, insect larvae and pupae. Estimates of daily food intake were based on two periods of intense feeding (early morning and late afternoon). Fish egested 39% of the food consumed during a single feeding period. Mean caloric content of this material was 3,339 and 3,760 g˙cal/g dry weight for laboratory and field samples, respectively. Measurements of the oxygen consumption of groups of fish fed meals of live zooplankton were used to calculate the energy of respiration. Oxygen consumption values were converted to gram-calories with an oxycaloric coefficient of 3.42 g˙cal released/rag oxygen consumed. Changes in the total energy content of fish were determined by converting increases in dry weight to their caloric equivalents. Daily food energy consumed by the fish represented about 6% of their total caloric content. Of this, roughly 27% was egested, while the remainder was assimilated and apportioned to growth and maintenance. Ecological growth efficiency was 32.0% during a 36-day period in 1967 and 22.5% during a 40-day period in 1968. The corresponding tissue growth efficiencies were 47.8 and 33.3%. Assimilation efficiency during the two periods averaged about 67%. Possible causes of the observed differences in growth efficiency are discussed.
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Thomas E. Wissing (1974) studied this question.