Energy budget
Encyclopedia
An energy budget is a balance sheet of energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 income
Income
Income is the consumption and savings opportunity gained by an entity within a specified time frame, which is generally expressed in monetary terms. However, for households and individuals, "income is the sum of all the wages, salaries, profits, interests payments, rents and other forms of earnings...

 against expenditure. It is studied in the field of Energetics
Energetics
Energetics is the study of energy under transformation. Because energy flows at all scales, from the quantum level to the biosphere and cosmos, energetics is a very broad discipline, encompassing for example thermodynamics, chemistry, biological energetics, biochemistry and ecological energetics...

 which deals with the study of energy transfer and transformation from one form to another. Calorie
Calorie
The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...

 is the basic unit of measurement. An organism in a laboratory experiment is an open thermodynamic system, exchanging energy with its surroundings in three ways - heat, work and the potential energy of biochemical compounds.

Fishes, like all organism, use ingested food resources (C=consumption) as building blocks in the synthesis of tissues (P=production) and as fuel in the metabolic process that power this synthesis and other physiological processes (R=respiratory loss). Some of the resources are lost as waste products (F=faecal loss, U=urinary loss). All these aspects of metabolism can be represented in energy units. The basic model of energy budget may be shown as:


P = C - R - U - F or



P = C - (R + U + F) or



C = P + R + U + F


All the aspects of metabolism can be represented in energy units (e.g. joules (J);1 food calorie
Calorie
The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...

 = 4.2 kJ).
Energy used for metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

will be


R = C - (F + U + P)


Energy used in the maintenance will be


R + F + U = C - P


The compilation of energy budget for fish has a fairly short history, with the result that literature on the subject is limited.
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