POND© Tutorial
Shree S. Nath, John P. Bolte and Doug Ernst
Biosystems Analysis Group, Department of Bioresource Engineering
Oregon State University, Corvallis, OR 97331, U.S.A
The POND software and supporting documentation has been developed
under a grant from the Pond Dynamics /Aquaculture Collaborative
Research Support Program (PD/A CRSP), funded in part by the U.S.
Agency for International Development, Grant No. DAN-4023-G-00-0031-00.
We acknowledge the assistance of Gholam R. Moosapanah in the preparation
of this tutorial.
The contents of this document do not necessarily represent an
official position or policy of the U.S. Agency for International
Development. Also, the mention of trade names or commercial products
does not constitute endorsement or recommendation for use on the
part of the U.S. Agency for International Development or the PD/A
CRSP. All products, names, and services are trademarks or registered
trademarks of their respective companies.
Although every precaution has been taken in the preparation of
the POND software, Oregon State University as well as the PD/A
CRSP assume no responsibility for errors or omissions, nor is
any liability assumed for damages resulting from the use of the
information generated by the software.
For technical assistance, or to forward any comments/suggestions, please contact:
Dr. John Bolte
Department of Bioresource Engineering
Gilmore Hall, Oregon State University
Corvallis, OR 97331, U.S.A
Phone: (541) 737-6303 or (541) 737-3218. Fax: (541) 737-2082
The POND software is copyrighted to Oregon State University.
The POND tutorial will primarily focus on applications of the
software, which was written to provide educators, extension agents,
pond managers and researchers with a tool for rapidly exploring
the effects of various management practices on facility-level
performance and economic returns. This functionality is accomplished
primarily by the use of simulation models and an
economic analysis package.
Production scenarios that can be explored using POND include: site locations, fish species for culture, stocking densities, feeding rates, fertilization rates, liming rates, and water exchange rates.
The objectives of the POND tutorial are as follows:
This section deals with basic information required for a proper
understanding of the concepts and terminology used in the POND
software. A brief review of the POND models and software installation
is also provided. Please refer to User's Guide or to the on-line
help system for more detailed information.
To effectively apply POND in planning and managing an aquaculture
facility, it is useful to be familiar with the concept of a system.
In general, a system may be defined as a collection
or arrangement of components that are related in such a way as
to form a whole. A change in any component is reflected in the
behavior of the whole. A facility represents a system because
a change in any component (e.g., site location, pond characteristics)
will cause the overall behavior to change. In POND,
the term facility represents an existing or planned pond
aquaculture system consisting of the following entities:
These facilities are 'created' in POND by accessing various databases.
Management practices can also be defined by manipulating information
stored in these databases.
Once a facility and associated management practices have been
specified in POND, the program can be used to forecast or predict
changes in the system over time. For example, fish growth during
the time period between the date of stocking and anticipated date
of harvest can be predicted. This type of prediction is accomplished
by the use of simulation models, which are useful tools
to describe systems.
Simulation Models: POND contains simulation models that
describe various components of a pond aquaculture system. A simulation
model is essentially a collection of mathematical expressions
that describe relationships among components within the system
of interest.
State Variable: Each component of a simulation model is
typically represented as a state variable, which describes
the current state of that component at any given time. For example,
pond water temperature can be considered to be a state variable.
The state variables in the POND simulation models require an initial
value to be provided by the user. The collection of all these
values describes the initial conditions of the pond aquaculture
system.
Time Step: The mathematical expressions in a simulation
model are typically set up to describe changes that occur to the
relevant state variables over a small time interval which is called
the time step. This rate change is mathematically solved
by POND for the overall simulation period
to arrive at the final state of the system.
Parameter: The rate of change of a state variable is a
result of various processes that are considered in the mathematical
expression for the particular variable. The rate expressions for
these processes typically involve the use of a quantity or constant
whose value can be varied depending on the circumstance of its
application. This constant is referred to as a parameter.
Compartment Modeling: Compartment modeling is a way of
viewing subsets of a given system. For example, a pond can be
considered to have two compartments: (a) the pond water compartment,
and (b) a sediment compartment. Each compartment can maintain
relevant state variables.
Dynamics & Kinetics: The term
dynamics applies to a system that continually changes.
Kinetics has a similar meaning, but is more commonly
used to describe changes that occur in certain biological populations
(e.g., bacteria) or nutrient pools (e.g., nitrogen, phosphorus).
Steady State: When a state variable is said to follow steady
state kinetics, it implies that the rate change is zero. In
other words, the net change in the state variable over time is
zero. For example, if the nitrogen concentration in a pond is
assumed to follow steady state kinetics, it implies that the concentration
remains constant throughout the period of simulation.
The purposes of the POND simulation models are as follows:
POND simulation models are organized hierarchically into three
levels based on increasing complexity. Each modeling level has
different data requirements and can be used to conduct different
kinds of analyses:
NOTE: We will not be dealing with Level 3 models in this
tutorial.
The main purpose of the economic analysis package is to allow
rapid assessment of different pond configurations or management
scenarios that can be simulated by the models in POND. Economic
analysis capabilities in POND are provided in the form of enterprise
budgeting.
An enterprise budget is essentially a tabulation of the costs
and income for a farm operation. The three categories of costs
supported in POND are:
Depreciable Costs: For items which are purchased for long-term
use and then depreciated over the lifetime of service for the
item. Examples include pumps, heavy equipment, and buildings.
Fixed Costs: For items which incur a known, constant expense
over the multiple periods of analyses. Examples include land and
pond construction costs.
Variable Costs: For items which incur costs that vary with
factors such as the amount of production and type of management.
Examples include costs for fingerlings, fertilizers, feed, and
fuel.
Income streams in POND typically include only marketable
fish, although income that accrues from other items produced (e.g.,
crops produced in an integrated agriculture-aquaculture farm),
if any, can be optionally considered.
POND requires a IBM-compatible personal computer running the Microsoft
Windows (version 3.1 or higher) operating environment. It requires
approximately 1.5MB of available hard disk space and a minimum
of 4MB RAM. A 80386 CPU is required, and a 80486 or greater CPU
is recommended.
POND comes on a single 3.5" floppy disk. The simplest way
to install POND is to make a directory on your hard disk using
the DOS md command as follows:
> md c:\pond
Once the POND files are copied to your hard
disk, start Windows by typing Win at the DOS prompt.
Next, set up a Program Manager group for POND.
This is accomplished by selecting File/New from
the Program Manager main menu and selecting Program Group.
This will create a POND group.
Then, select File/New from the main menu, select
Program Item, and specify POND.EXE and C:\POND in the Command
Line and Working Directory fields, respectively. Once
the program item is established, double-click on the POND icon
to start the program.
Basic user interaction with the databases is handled in a consistent
manner across all databases. All databases share the following
characteristics:
To edit the database, select the appropriate
database from the Parameters menu or push the appropriate
toolbar button. The dialog interface window will appear. A number
of functions are common across all database editing dialogs, as
described below.
Browsing Records
Records in the database can be traversed by selecting the <<
and >> buttons, or by scrolling directly through
the list of record names.
New records can be add to the database by selecting the <Add>
button. A blank (default) record will appear for editing. Alternatively,
you may make a copy an existing record by selecting the <Copy>
button. In either case, you will be requested to provide a name
for the new record.
Existing records are removed from the database by selecting the
<Remove> button. The currently selected
record will be removed from the database.
When you are finished viewing and/or modifying pond records, you may select the <OK> button to use the updated values (without saving the changes permanently to your disk), or select the <Save to Disk> button to use the changes and save them permanently to your disk. Use the <Cancel> button to ignore any changes made to the current record.
On-line help in POND is obtained by selecting the <Help>
button in the various dialog boxes of the program. This operation
accesses the relevant section of the User's Guide.
The POND program contains 12 primary databases, as indicated in the table below. The table also indicates the pages in the User's Guide where complete details relevant to the use of these databases can be obtained. Use the information in the Guide or access the on-line help system to fully explore the databases.
| Source Water | |
| Ponds | |
| Fish Lots | |
| Fish Species | |
| Site Information | |
| Soil Characteristics | |
| Fertilizer Characteristics | |
| Feed | |
| Liming Material Characteristics | |
| Weather | |
| Economics | |
| Simulation Setup and Control |
This section deals with two options in POND that can be used to
determine fertilizer and lime requirements for individual ponds
without the use of simulation models.
POND calculates weekly nutrient (nitrogen, phosphorus and carbon)
requirements for a pond based on water quality data entered in
the Pond database and a simple model of phytoplankton growth.
After selection of one or more fertilizers from the Fertilizer
database, the program then calculates the quantity of a single
fertilizer (if only one fertilizer type is specified) or the least-cost
combination of different fertilizers needed to meet these nutrient
requirements of the pond.
To access the fertilizer requirements utility, follow the steps
below (for complete details, refer to pgs. 44-49 of the User's
Guide or access the on-line help system):
POND contains a utility which allows users to estimate the static
lime requirements for individual ponds in a facility on the basis
of soil properties. These lime requirements may be more appropriate
for newer ponds, rather than those that have been in operation
for many years. Lower amounts of lime may suffice for the latter
category of ponds.
To access the lime requirements utility, follow the steps below
(for complete details, refer to pg. 50 of the User's Guide or
access the on-line help system):
POND simulations involve three main phases:
These phases are demonstrated in the trial simulations below.
More complete details can be obtained by referring to Chapter
5 of the User's Guide (pgs. 51-57).
Note that economic analysis can be conducted after a simulation
run by generating an enterprise budget. We will deal with this
issue (Section 2.4) after completing the simulation phases.
The hypothetical facility has the following general characteristics.
The above facility will first be simulated by the use of Level
1 models. An enterprise budget for this trial simulation will
then be generated. The procedure will be repeated for a Level
2 simulation.
NOTE: The required data have already been entered
into the POND databases.
| Site | Romsai, Thailand |
| Weather | From file - romsai.wdb |
| Source water | Canal |
| Pond | 2 ponds |
| Lots | 1 lot per pond |
| Species | Nile tilapia (Oreochromis niloticus) |
The simulation scenario is created as follows:
Clock Settings
This is used to define the period of simulation. Use the following settings:
Start time: January 15th, 1996
Stop time: August 15th, 1996
Time step: Daily (1 day for a Level 1 simulation;
0.1 day for Level 2)
Parameter Setup
Set the simulation level to Level 1. Then, push the <Level
1 Options> button to view the fertilizer schedule set for
the Romsai ponds. Skip Section 2.3.1B and proceed from the Set
Ponds to Simulate part below.
Set the simulation level to Level 2. Then, push the <Level
2 Options> button to view the Level 2 Model Parameters
dialog box. Other model options can be viewed by pushing the <Nutrient
Thresholds>, <Other Sources and Sinks> and/or
<Zooplankton Parameters> buttons.
Set Ponds to Simulate
Push the <Select Ponds> button. From the list of
available ponds, select Romsai-1 and Romsai-2 into the list to
be simulated by pushing the Add button.
Results
Retain the default settings.
Once the simulation scenario has been created as described above,
simply push the <Run> button at the bottom left corner
of the Pond Simulation Control dialog box. The Progress
box indicates the extent to which a simulation is completed. Proceed
to Section 2.3.3 when the simulation has been completed.
Simulation results are available in the form of an overall summary
or model output plots.
To accomplish the optimization, select the available fertilizers
from the list in the Fertilizer Requirements Setup dialog
box. Then, push the <Run Optimizer> button and view
the fertilizer recommendations.
Push the <Plot> button from the Pond Simulation
Control dialog box OR push the <Plot> icon on
the toolbar. This brings up the Select Graph Items dialog
box.
The Data Source indicates the source of the simulation
data that can be plotted. Select the Lot RL-1. A list of items
associated with this lot are shown under the Variables
list box. From this list, select the item "Fish Weight (g)".
Next, choose the pond Romsai-1 from the Data Source list
and select the item "Water Temperature (°C)".
Push the <OK> button to view plots of the selected
items. Plots can be closed by double-clicking on the top left
corner of the relevant window.
NOTE: Repeat the above procedure for other items
of interest.
POND provides economic analysis capability in the form of enterprise
budgeting to allow rapid assessment of different pond configuration
or management scenarios that can be created in POND.
The cost database provides information that is fed to the economics
package in POND, which can be used to generate enterprise budgets
upon completion of a simulation.
In POND, cost and income data for the enterprise budgets include
simulation and non-simulation items:
After completion of the simulation, select the Economics
menu item and then Generate Summary Budget option. POND
provides three options for calculating production costs and income:
(i) facility, (ii) unit area, and (iii) unit
production basis.
Selection of any of the above options results in the Economic
Summary Sheet being displayed. If the 'Facility basis' is
selected, the enterprise budget will reflect costs and income
for the overall facility (one or more ponds). Similarly,
if the 'Unit Area' option is selected, budget calculations are
based on a per unit area (e.g., per ha) basis. Finally,
if the 'Unit production' option is selected, budget calculations
are based on a per unit of production (e.g., per kg of
fish) basis.
Individual fields in the summary sheet can be updated by direct
editing, or by editing data in the Cost database. This database
can be obtained by double clicking any field in the summary sheet.
We need to add/edit several items in the Cost database to reflect
facility/site specific information:
Fingerling Costs: Push the <Lots> toolbar
button, select RL-1 or RL-2 and note the number of fingerlings
required based on the stocking density. Create a new record in
the Cost database with the name "Fingerlings", enter
the number of fingerlings and set the Cost basis to "Per
Unit of Area".
Fertilizer Costs: POND automatically calculates the nutrient
requirements for the ponds that were simulated. However, it is
necessary to translate these requirements into actual fertilizer
amounts. To accomplish this task, the following steps are required:
Poultry litter 0.25 Baht/kg
Urea 7.00 Baht/kg
TSP 12.00 Baht/kg
NOTE: Repeat step (g) above for each of the fertilizers in the least-cost combination.
Liming Costs: We will assume that the simulated ponds were
limed at the beginning of the culture period. To calculate the
lime requirements, we need to repeat the procedures used in Section
3.2.2. The procedures are as follows:
From the Cost database, push the <OK> button
to generate a completed enterprise budget for the facility.
The use of POND to address issues relevant to pond aquaculture
management will be demonstrated using the following problem sets:
Two ponds (Bang Sai-1 and Bang Sai-2) from a Nile tilapia (Oreochromis niloticus) facility in Thailand have been selected for this problem. The following assumptions are made:
To access the weekly fertilizer recommendations utility, follow
the steps below (for complete details, refer to pgs. 44-49 of
the User's Guide or access the on-line help system):
Poultry litter 0.25 Baht/kg
Urea 7.00 Baht/kg
TSP 12.00 Baht/kg
| Scenario 1
Gross Primary Productivity Nutrient sources and sinks: Nitrogen Phosphorus | 5 gC m-3 d-1 80% 70% |
| Scenario 2
Gross Primary Productivity Nutrient sources and sinks: Nitrogen Phosphorus | 3 gC m-3 d-1 90% 60% |
To access the lime requirements utility, follow the steps below
(for complete details, refer to pg. 50 of the User's Guide or
access the on-line help system):
| Scenario 1
Soil type Use Soil pH to calculate PBS Liming source | Coarse loamy Check Limestone |
| Scenario 2
Soil type Use Soil pH to calculate PBS Soil pH Liming source | Coarse loamy Uncheck 5.5 Limestone |
| Scenario 3
Soil type Use Soil pH to calculate PBS Soil pH Liming source | 1:1 Clayey Uncheck 5.5 Quick Lime |
Fertilizer requirements
Did the nutrient and fertilizer requirements change with the different
scenarios? If so, in what way?
Are there any changes in fertilizer recommendations (composition
and costs)?
Lime requirements
Did the lime requirements change with the different scenarios?
If so, in what way? Are there any changes in costs?
Four ponds (Fishery-1 to 4) from a channel catfish (Ictalurus punctatus) facility in California have been selected for this problem. The following assumptions are made:
We will use the Level 1 simulation modeling options to run the
following scenarios:
The facility has the following general characteristics:
NOTE: The required data have already been entered
into the POND databases.
| Site | Fishery (Sacramento) |
| Weather | Generated |
| Source water | N/A |
| Pond | 4 ponds |
| Lots | 1 lot per pond |
| Species | Channel catfish (Ictalurus punctatus) |
The simulation scenario is created as follows:
Clock Settings
This is used to define the period of simulation. Use the following settings:
Start time: April 15th, 1996
Stop time: November 15th, 1996
Time step: Daily (1 day)
Parameter Setup
Push the <Fish Lot(s)> button to view the Lot database. Relevant lots for our trial simulations are FL-1 to 4.
For all the lots, set the feed type to "low quality feed"
and satiation feeding level to 50%.
For all the lots, set the feed type to "high quality feed"
and satiation feeding level to 75%.
Set Ponds to Simulate
Push the <Select Ponds> button. From the list of
available ponds, select Fishery-1 to 4 into the list to be simulated
by pushing the Add button.
Results
Retain the default settings.
Once the simulation scenario has been created as described above,
push the <Run> button at the bottom left corner of
the Pond Simulation Control dialog box.
Summary Results
Push the <Summary> button at the bottom of the Pond Simulation
Control dialog box to view the Pond Summary Results
dialog box. The summary dialog displays results on a pond by pond
basis. Check the Show All box to scroll through individual
ponds.
| FL-1 | ||
| FL-2 | ||
| FL-3 | ||
| FL-4 |
Plotting Results
Push the <Plot> button from the Pond Simulation
Control dialog box OR push the <Plot> icon on
the toolbar. This brings up the Select Graph Items dialog
box.
The Data Source indicates the source of the simulation
data that can be plotted. Select the Lot FL-1. A list of items
associated with this lot are shown under the Variables
list box. From this list, select the item "Fish Weight (g)"
and "Lot feed rate (%bw/day)".
Next, choose the pond Fishery-1 from the Data Source list
and select the item "Water Temperature (°C)".
Push the <OK> button to view plots of the selected
items. Retain the fish weight and lot feeding rate plots after
Scenario 1 has been run.
Are the predicted feed requirements different for the two scenarios?
If so, in what way?
Four ponds (EAP-1 to 4) from a Nile tilapia (Oreochromis niloticus) facility in Honduras (Central America) have been selected for this problem. The following assumptions are made:
We will use the Level 1 simulation modeling options to run the
analysis.
The facility has the following general characteristics:
NOTE: The required data have already been entered
into the POND databases.
| Site | EAP, Honduras |
| Weather | From file - eap.wdb |
| Source water | Canal |
| Pond | 4 ponds |
| Lots | 1 lot per pond |
| Species | Nile tilapia (Oreochromis niloticus) |
The simulation scenario is created as follows:
Clock Settings
This is used to define the period of simulation. Use the following settings:
Start time: October 1st, 1995
Stop time: March 30th, 1996
Time step: Daily (1 day)
Parameter Setup
For all the EAP ponds, ensure that the Use Water Balance
box is checked.
For all the EAP ponds, ensure that the Use Water Balance
box is unchecked.
Push the <Simulation> button to view/edit the Simulation
database. Set the simulation level to Level 1.
Set Ponds to Simulate
Push the <Select Ponds> button. From the list of
available ponds, select EL-1 to 4 into the list to be simulated
by pushing the Add button.
Results
Retain the default settings.
Once the simulation scenario has been created as described above,
push the <Run> button at the bottom left corner of
the Pond Simulation Control dialog box.
Summary Results
Push the <Summary> button at the bottom of the Pond Simulation
Control dialog box to view the Pond Summary Results
dialog box. The summary dialog displays results on a pond by pond
basis. Check the Show All box to scroll through individual
ponds.
| EAP-1 | ||||
| EAP-2 | ||||
| EAP-3 | ||||
| EAP-4 | ||||
Plotting Results
Push the <Plot> button from the Pond Simulation
Control dialog box OR push the <Plot> icon on
the toolbar. This brings up the Select Graph Items dialog
box.
The Data Source indicates the source of the simulation
data that can be plotted. Select the Lot EL-1. A list of items
associated with this lot are shown under the Variables
list box. From this list, select the item "Fish Weight (g)".
Next, choose the pond EAP-1 from the Data Source list and
select the items "Water Temperature (°C)", "Daily
N Req", "Daily P Req", "Total N Req"
and "Total P Req". Plot "Pond Volume" and
"Total Water requirements" as well.
Push the <OK> button to view plots of the selected
items. Retain the pond related plots after Scenario 1 has
been run.
After completion of the simulation, select the Economics
menu item and then Generate Summary Budget option. We will
use the 'Facility basis' option for the analysis.
We need to add/edit several items in the Cost database to reflect
facility/site specific information:
Fingerling Costs: Push the <Lots> toolbar
button, select any of the EL lots and note the number of fingerlings
required based on the stocking density. Proceed to the Cost database
and for the record "Fingerlings", enter this number
and set the Cost basis to "Per Unit of Area".
Fertilizer Costs: POND automatically calculates the nutrient
requirements for the ponds that were simulated. However, it is
necessary to translate these requirements into actual fertilizer
amounts. To accomplish this task, the following steps are required:
Select poultry litter, urea and triple superphosphate into the list of Fertilizers to Consider. For each of these fertilizers, use the <Edit Fertilizers> button and set the cost as indicated in the table below.
NOTE: Repeat step (g) above for each of the fertilizers in the least-cost combination.
Other Costs/Income: Other costs for the EAP facility should be entered into the Cost database using the information below.
| Income
Fish harvested (lots) |
kg | 8.00 |
| Fixed Costs
Pond Construction |
-- | 10000 |
| Depreciation
Equipment Buildings | -- -- | 5000 10000 |
| Variable costsb
Fingerlings Urea TSP Poultry litter Wages Transportation | Each kg kg kg Total Total | 0.10 1.53 1.82 0.10 6000.00 800.00 |
| Net Returns |
Are the predicted fertilizer requirements different for the two
scenarios? If so, in what way?
Are there any cost differences between the two scenarios?
The simulation modeling and enterprise budgeting capabilities
of POND can be used to optimize management practices for a given
facility. For example, if it is desired to maximize net returns,
multiple simulation runs with different combinations of management
practices can be conducted and enterprise budgets generated. The
combination resulting in the highest net returns should be optimal.
The objectives of this problem are as follows:
We will assume a four pond facility (one lot per pond) at Romsai,
Thailand where Nile tilapia (Oreochromis niloticus) is
cultured. For simplicity, we will also assume that two intensities
of each management practice are possible as defined below:
| Stocking Density | Low (L)
High (H) | 10000 fish ha-1
30000 fish ha-1 |
| Feeding | Low
High |
50% satiation
75% satiation |
| Fertilization | Low
High | GPPa = 3 gC m-3 d-1
GPP = 5 gC m-3 d-1 |
a GPP refers to the potential gross primary productivity
for the site.
There are a total of eight unique combinations that need to be
evaluated:
| |||||
a This refers to the critical standing crop for the lots, a parameter that is assumed to be a function of pond fertilization.
b Enter this information after running simulations
and generating enterprise budgets as described in Section 4.4.3
below.
We will use the Level 1 simulation modeling options to run the
analysis. The steps are briefly described below. If necessary,
refer to the previous problems where further setup details are
provided.
The procedure to be followed is as follows:
After completion of each simulation, select the Economics
menu item and then Generate Summary Budget option. We will
use the 'Per Unit Area' option for the analysis. We need to add/edit
several items in the Cost database to reflect facility/site specific
information:
Fingerling Costs: Push the <Lots> toolbar
button, select any of the RL lots and note the number of fingerlings
required based on the stocking density. Proceed to the Cost database
and for the record "Fingerlings", enter this number
and set the Cost basis to "Per Unit of Area".
Fertilizer Costs: POND automatically calculates the nutrient requirements for the ponds that were simulated. However, it is necessary to translate these requirements into actual fertilizer amounts. To accomplish this task, the following steps are required:
Select poultry litter, urea and triple superphosphate into the list of Fertilizers to Consider. For each of these fertilizers, use the <Edit Fertilizers> button and set the cost as indicated in the table below.
NOTE: Repeat step (g) above for each of the fertilizers in the least-cost combination.
Other Costs/Income: Other costs for the Romsai facility should be entered into the Cost database using the information from the table below.
| Income
Fish harvested (lots) |
kg | 12.00 |
| Fixed Costs
Pond Construction |
-- | 10000 |
| Depreciation
Equipment Buildings | -- -- | 3500 7500 |
| Variable costsb
Fingerlings Urea TSP Poultry litter Feed Wages | Each kg kg kg kg Total | 0.10 7.00 12.00 0.25 6.00 5000.00 |
How do the costs compare among the eight scenarios?
Which scenario (if any!!) would you consider using if you are
a pond facility planner/manager? Why?
We will work with the Level 2 models if time permits. The procedures
outlined in Section 3.3 will be used and a more detailed explantion
will be provided by the instructor.
This section may be useful to people already familiar with concepts of pond modeling and the POND software. The topics include:
Developing nutrient budgets for pond systems is useful from the
viewpoint of understanding the fate of exogenous material (e.g.,
feeds, fertilizers, etc) added to ponds and assessing potential
impacts of pond aquaculture on the surrounding environment.
Nutrient (carbon, nitrogen and phosphorus) gain or loss in Level 2 POND models occur in the following components:
The general approach to analyzing nutrient budgets is to create a Level 2 simulation scenario and execute the models. The budgets for the particular scenario can then be analyzed graphically.
This is done by plotting the relevant rates for each nutrient
available in the list for the pond simulated to observe changes
over time.
Fish growth can be limited by temperature, low dissolved oxygen
or high ammonia concentrations. Similarly, phytoplankton and bacterial
growth are limited by nutrient supply and temperature. Phytoplankton
growth may also be further limited by the availability of light.
Effects of these limiting factors can be modeled in a variety
of ways.
We will examine two scenarios relating to effects of phosphorus
concentrations on phytoplankton growth to illustrate the concept
of limiting factors.
Repeat steps 1-6 above with the exception that at step 4, uncheck
the box next to 'Phosphorus'. This will ensure that fertilizer
requirements for the Level 2 model will be estimated on the assumption
that phosphorus is not limiting.
Compare the plots generated under scenarios 1 and 2.
Users may often be interested in applying POND models to fish
species, parameters for which are not available in the software.
To address this need, we provide a parameter estimation package
within the software that automatically generates appropriate parameters
for a given species. Refer to Chapter 6 (pgs. 58-61) of the User's
Guide or access the on-line help system for further details.
Use of the package requires details about the facility. In particular,
fish growth profiles (fish weights at different time intervals
over a culture period) for the species and details of management
practices (stocking densities and initial weights, fertilizer
and feeding rates) are needed. Water temperature and weather information
are also useful.
This section briefly discusses limitations of POND and other model-based decision support tools.
In general, although simulation models are useful tools for understanding
complex models, they are abstractions of reality and may not provide
enough information for routine management.
Some of the other limitations of POND and its models include:
Copyright © 1996 Biosystems Analysis Group, Oregon State University