Computer simulation program VIJVER (or FISH POND or FOOD CHAIN)

Due to the relatively simple tropic structure a fish pond can be an excellent case for the study of the characteristics of food-chains and ecosystems in general. However, fish ponds can not be studied in the biology curriculum for practical reasons (space and time). A computer simulation program, simulating a fish pond, can be an excellent tool to overcome these problems.

For this reason a mathematical model of a fish pond can serve two purposes: fish pond management and education. The model constructed by Svirezhev et al (1984) simulates a fish breeding pond in which three fish species are present: carp, silver carp and bighead carp (see figure 7.1). Van Schaick Zillesen adapted the model for a pond in which only two fish species are present (carp and silver carp).

The program FOOD CHAIN is based on the adapted version of the model of Svirezhev et al. Svirezhev et al. (1984) give values the parameters used in their model. However, they do not give starting values for the variables of the model. Labordus (National Institute for Curriculum Development) gathered the data about the values of these variables from literature.

Educational value

The prototype VIJVER (FOOD CHAIN) is designed for students in secondary education and lower vocational training. Before the start of the simulation, students should have advance knowledge of ecological processes in the fish pond. This advance knowledge is reinforced during the use of the simulation program.

Figure 7.1 The model of the computer simulation program VIJVER. (Svirezhev, et.al., 1984)

Before the start of the simulation the students should be aware of the following ecological processes:

• Plants require minerals, water, carbon dioxide and oxygen.
• Green plants (producers) synthesize organic material during photosynthesis. Light is required in order to do this. Oxygen is produced during photosynthesis.
• For their food animals (consumers) depend on plants (directly or indirectly).
• Within an ecosystem, several (long and short) food-chains and food-webs may exist.
• Plants, animals and man produce organic material.
• The organic material is mineralized by bacteria and fungi (reducers).

Apart from the reinforcement of this knowledge, the program is also used to teach new phenomena like:

• The growth of plants is determined not only by the presence of water, carbon dioxide, light and minerals, but also by the ratio in which these prerequisites are available.
• A wealthy growth of plants leads to an increase in the quantity of animals.
• When two animal species use the same food an equilibrium between the two species and their food will develop.
• In a complex system such as a pond an equilibrium gradually develops between all species present and the abiotic conditions. If these are changed a different equilibrium will evolve.
• Computer simulation programs can be applied for prediction, research, learning, gaming and management.
• The skill to work with abstract representations of systems and processes, like dynamic graphs and diagrams is trained by working with the program.
• The skill to test hypotheses by means of active experimentation is trained by working with the program.

The prototype can simulate five ponds. In each pond oxygen, nitrate, phosphate and detritus (a complex of organic material and fungi and bacteria) are present. The following ponds can be simulated:

• Pond 1 (Algae). In this pond phytoplankton (algae) is present.
• Pond 2 (Silvercarp). In this pond phytoplantkon is present as well as silver carp.
• Pond 3 (Zooplankton and Benthos). In this pond the following organisms are present: phytoplankton, zooplankton and benthos.
• Pond 4 (Carp). In this pond the following organisms are present: phytoplankton, zooplankton, benthos and carp. See figure 7.2

Figure 7.2 Input window of the computer simulation program VIJVER with the conceptual model of a fishing-pound according to Svirezhev et.al.

Pond 5 (Fish Pond). In this pond the following organisms are present: phytoplanton, zooplankton, benthos, carp and silver carp. A student studying this pond is able to feed the fish with artificial fodder. Furthermore, he or she can re-aerate the water in the pond.

The program has been used in many levels of education varying from lower vocational training to a university course.
In lower vocational training only the most simple ponds (pond 1 and pond 2) are studied. The other ponds are too complicated to be understood by the students.
In secondary education all ponds can be studied. However, ponds 2, 3 and 4 are rather similar to each other. Because of this one or two of these ponds are usually skipped.

Hartsuijker et al. (1989) developed paper materials, which can be used in combination with the simulation program. Their publication consists of the following parts:

• students' leaflets with information about the subject matter, information about the control of the program and exercises.
• a teacher's guide with information about the educational goals of the program, the required advance knowledge of the students, answers to the exercises on the students' leaflets, characteristics of all ponds and an installation manual.

A complete computer simulation supported learning environment can be constructed by combining the educational computer simulation program with the paper materials.

Description

The program FOOD CHAIN, version MacTHESIS, is designed by Van Schaick Zillesen, (1988) according to the description of the students' learning environment of MacTHESIS.
In this application four windows are present:

In the first window the internal structure of the simulated pond is visualized by means of a diagram. The values of the main variables are indicated in the diagram by means of digits. Day and night conditions are indicated by means of animation techniques. Students can change the values of parameters and variables in the model by clicking in the grey rectangles in the diagram. In each pond different interventions are possible:

• pond 1: quantity of algae, fertilization by means of phosphate, fertilization by means of nitrate.
• pond 2: quantity of algae, fertilization by means of phosphate, fertilization by means of nitrate, quantity of silver carp.
• pond 3: quantity of algae, fertilization by means of phosphate, fertilization by means of nitrate, quantity of zooplankton, quantity of benthos.
• pond 4: quantity of algae, fertilization by means of phosphate, fertilization by means of nitrate, quantity of zooplankton, quantity of benthos, quantity of carp.
• pond 5: quantity of algae, fertilization by means of phosphate, fertilization by means of nitrate, quantity of zooplankton, quantity of benthos, quantity of carp, quantity of silver carp, quantity of fodder, quantity of re-aeration.

The second window contains time registrations of the quantities of phytoplankton, oxygen, nitrate and phosphate in the pond.
The third window contains time registrations of the quantities of carp, silver carp, zooplankton and benthos in the pond.
The fourth window contains a time registration of the quantity of detritus in the pond.

Students may intervene with the model by means of the input-animation technique as described earlier. Furthermore, the same interventions are possible by means of the menu bar.
At the start of the program pond 1 is presented to the student. The other ponds can be selected by means of the menu bar. There is a MS.DOS version of the program FOOD CHAIN available. Since 2001 there are some online internet versions of the program FOOD CHAIN available (see figure 7.3, 7.4 and 7.5).

Figure 7.3 The output of the computer simulation program VIJVER / FOOD CHAIN (on the internet) (during xx days) (intervention with phosphate and nitrate that starts on day 4) (the red curve is increasing: the amount of phytoplankton, 'algen' or 'F') (the yellow curve is first increasing and than decreasing: the amount of oxigen or 'O') (Min c.s., 2004)..

===> <===

Enschede, 1995; splitted & updated febr. 3, 2005. Gerestaureerd in 2020

Note: This chapter is first published by P.G. van Schaick Zillesen in his Ph.D thesis at the University of Twente, Enschede. Edited by F.B.M. Min.

References

Schaick Zillesen, P.G. van, and F.B.M. Min, (1988). Een R. & D. project in de onderwijskunde; een computersimulatiesysteem voor VWO en MBO. In: Onderwijskundige technologie: modellen & emperie (Red. P.H. Been & K.B. Koster) Swets & Zeitlinger, Lisse.