Literary processing of materials on nutrition

Depending on the objectives of the research, only partial indices and a percentage value by weight of various food components are indicated, or more complete data on the nutritional characteristics are given: in addition to private indices, “frequency of occurrence” should be given – the number of copies of food organisms on average per fish, maximum indices, maximum weights of food components and total food, maximum number of food organisms, and minimum, maximum and predominant sizes of organisms consumed by fish. All these data are summarized in the form of separate tables or columns of the general table from the available individual cards.

The results of digital processing of the material, in addition to tables, are presented in graphs of various shapes – in the form of circles, rectangles, curves, etc., and are also plotted on maps. The course of nutrition can be depicted in the form of curves for individual food components (Fig. 36); the importance of organisms in nutrition can be expressed in the form of rectangles (Fig. 37). The diagram in fig. 38 gives an idea of the change in the percentage of food components.

Rice. 36. Changes in the food composition of pike juveniles due to growth (in percent by weight):

1 – branched crayfish; 2 – copepods; 3 – chironomid larvae; 4 larvae of other insects; 5 – fish (size groups of juveniles correspond to the groups in Fig. 37)

Rice. Fig. 37. Changes in the food composition of juvenile pike due to growth (in percent by weight): 1 – cladocerans; 2 – copepods; 3 – chironomid larvae; 4 – larvae of other insects; 5 – fish

Rice. 38. Changes in the food composition of juvenile pike due to growth (in percent by weight). The designations are the same as in Fig. 37

On fig. 39 shows the feeding spectra of fish in the form of rectangles, the area of which corresponds to the general filling index of the gastrointestinal tract or the weight of the food bolus; the value of the individual components is expressed as a percentage of the total weight or of the total index.

Changes in the nutritional spectrum can be represented as shaded areas corresponding to the value of individual components in percent by weight (Fig. 40).

Rice. 39. Changes in the food composition of juvenile pike due to growth (in percent by weight). The designations are the same as in Fig. 37

Rice. 40. Changes in the food composition of juvenile pike due to growth (in percent by weight). The designations are the same as in Fig. 37

The most indicative and widespread graph is in the form of circles (Fig. 41). The area of the circle corresponds to the overall filling index of the digestive tract, the square root of which is equal to the radius of the circle. Separate sectors of the circle mean the weight of food components or private indices as a percentage of the total index (practically as a percentage of the circumference or 350 °). Such diagrams can graphically depict all aspects of fish nutrition: daily, seasonal, annual course of nutrition, nutrition by age, by individual sexes, etc.

Rice. 41. Changes in the food composition of juvenile pike due to growth (in percent by weight). The designations are the same as in Fig. 37.

On the basis of the obtained digital and graphic data, conclusions are drawn about the nature of fish nutrition, their feeding, possible competition in nutrition, the state of the food supply, etc.

Control questions and tasks

1. Give the concept of peaceful and predatory fish.

2. Intensity of nutrition (the degree of filling of the gastrointestinal tract).

3. Indices of filling and consumption.

4. Diets and food speed.

5. Food competition.

6. Feed ratio.

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