= = compact demonstration version = =

Fish pond / ecosystem / food chain

Fish pond ecosystem with carps & silvercarps, nutrients, zooplankton, benthos, dissolved oxygen, micro organisms in relation to spring, summer, autumn and a lot of other external variables and parameters.


Fish breeding pond; food chains.

Fish ponds are widely used by man for food production. The management of a fish pond, affects the entire ecosystem, including fish, nutrients, zooplankton, benthos, dissolved oxygen, microorganisms etc. A high efficiency of fish breeding can be achieved only with optimum values of the control parameters of the pond, like the input of fertilizers, the re-aeration of the water in case of oxygen depletion and the addition of artificial fodder. Svirezhev et al. (1984) developed optimum control strategies for a fish pond ecosystem. As part of their study they constructed a mathematical model of a fish pond. Van Schaick Zillesen designed and realised the computer simulation model FOOD CHAIN ('Viskweekvijver'). Later Rik Min develops the java applets for these sites.

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 model, 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 (xxx). 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 ('Viskweekvijver') 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.

The prototype FOOD CHAIN ('Viskweekvijver') 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.

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.

    Our model can simulate five different 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 only 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.
  • Pond 5 (Carps and Silvercarps). In this pond all things from other ponds, 1 to 4, come together.

    In this website you see two cases: pond 5 and with a link also pond 1. See the applet and the link along this point.

    Remark about Dutch versus English names:

  • Variables: 'Karpers' are Carps; 'Zilver K' ('zilverkarpers') are Silvercarps; 'Fosfaat' is phosphate; 'Nitraat' is nitrate; 'Zuurst' ('zuurstof') is dissolved oxygen;
  • Other variables: 'Wvlooien' ('watervlooien') are Water fleas; 'Bodemd' ('bodemdieren') are xxx; 'Algen' are Algae; 'Afval' is Garbage; 'Dag' is day and is the simulation time;
  • Parameters:. 'Visvoer' is Fodder; 'Zuurstof' is Oxygen; 'Fosfaat' is Phosphate; 'Nitraat' is Nitrate;

    Pond 5: Running the model: Changing parameters: Output:

    The time in the simulator is running 180 days: from April, 1 to September 30. Start is on day 91.
    (scratchpad)

    There are (here) 100 kg silvercarps (S), and 100 kg carps (C), in the pond (at time zero). The scales for F, O, C, N, P en D are 10 times higher than accoording the model itself.

    Assignments

    Assignment 1: Assignment 2:
    Assignment 3: Assignment 4:
    All assignments All answers

    Appendices

    (Background information)
    (Listing) (Analogue model)
    (Screendump 1992) (Screendump 2001) (Screendump 2003) (Screendump 2004)

    Enschede, Sept. 19, 2002; Acknowledgment: Piet v. SZ, JdG, JS, AH, Saskia Meulman, CW en AS. Updated in English: October 2004