fish culture managers. The size of the simulation time step is based on the nature of the aquaculture system and temporal resolution required to adequately capture
system dynamics. Daily simulations e.g. 1-day time step, for which diurnal variables and processes are expressed and used as daily means, always represent
some level of simplification at a degree depending on the type of facility and analysis resolution level. For example, all fish culture systems are at least character-
ized by diurnal fish process, resulting from day-versus-night activity levels and feeding rates of fish. However, diurnal simulations e.g. 1-h time step are required
only when the variability of process rates and state variables within a day period, and associated management responses, must be considered to adequately represent
the system. For example, diurnal simulations may be used for solar-algae ponds for high-resolution modeling of heat transfer and primary productivity, and they may
be used for intensive systems for high-resolution modeling of fish feeding and metabolism. Any consideration of process management within a 24-h period
requires diurnal simulations, e.g. pre-dawn aeration for pond-based systems or diurnal control of oxygen injection rates for intensive systems. For RK4 integra-
tion, daily simulations may require time steps of less than one day, but variables and processes are still used as daily means.
6. AquaFarm testing, calibration, and validation
The program code modules comprising AquaFarm were tested, debugged, and verified to perform according to the previously reported or newly developed
methods from which they were developed. Testing alone was sufficient to validate data input and output, management, and display tasks, integration procedures for
differential equations, and simulation of facility management. Similarly, the validity of actively managed processes was largely dependent on given process specifications
e.g. water treatment efficiencies and confirmed by direct testing. Finally, Aqua- Farm was verified to provide full ranges of expected results dependent variables
for all types of extensive and intensive aquaculture systems, solely by adjustment of input parameters and independent variables over their reasonable ranges. In sum,
this testing verified the internal and external consistency of AquaFarm Cuenco, 1989 and indicated sufficient development of the collected parameters, variables,
and unit processes considered and their combined expression as differential equa- tions and integrated functions.
Requirements for calibration and validation of the component models Cuenco, 1989 used in AquaFarm was variable, depending on the nature of these models
and their level of development in the supporting literature. Calibration is the process of determining values for model parameters equation coefficients and
exponents through regression procedures using empirical datasets. Due to the wide use of mechanistic models in AquaFarm, most parameters have inherent meaning
with respect to the processes they represent and can be directly estimated using reported values. Validation is the process of testing how much confidence can be
placed on simulation results. Calibration and validation accomplishments to date
are given in Appendix A. For some component models, these accomplishments are preliminary andor rely on parameter values from the supporting literature. Com-
pletion of calibration and validation procedures for selected, unit process models is ongoing, as described in the conclusion to this paper.
7. AquaFarm application
