D) Factors affecting the composition of fish

The composition of a particular species often appears to vary from one fishing ground to another, and from season to season, but the basic causes of change in composition are usually variation in the amount and quality of food that the fish eats and the amount of movement it makes. For example, fish usually stop feeding before they spawn, and draw on their reserves of fat and protein. Again, when fish are overcrowded, there may not be enough food to go round; intake will be low and composition will change accordingly. Reduction in a basic food resource, plankton for example, can affect the whole food chain. An example of how abundance of food supply can markedly change the composition of a species is shown by the sheepshead, an American freshwater fish: when taken from certain small lakes that were overstocked, the sheepshead had an average fat content of 1 per cent, compared with 6–10 per cent for those taken from rivers or lakes where food was plentiful.

Exercise 4. Find the Russian equivalents for the following:

commercial or legal requirements, to be tightly bound to the proteins, variation in the amount and quality, to be overstocked, to be plentiful, to vary from one fishing ground to another, extractive compounds, to change during storage, to be stored after capture, detailed analyses, measurement of the amount, to estimate the condition of the fish, uniformly distributed throughout the flesh, to be overcrowded, reserves of fat and protein, substances chemically related to, the total vitamin intake, characteristic of particular species, by careful processing.

Exercise 5. Find the English equivalents for the following:

запасы жира и белка, изменения в составе, быть важным для потребителя, важный вклад, сравнительно маленькие молекулы, азотная основа, основной компонент, содержание углеводов, витамины и минералы, жирорастворимые витамины, треска, палтус, белая рыба, жирная рыба, пресноводная рыба, морская рыба, хорошо сбалансированный, различия в количестве и качестве, фосфор, кальций, йод, аминокислота.

Exercise 6. Complete the sentences using information from the text:

1. Furthermore, if a diet is to be fully and economically utilized,…

2. When fish is stored after capture…

3. The vitamin content of individual fish of the same species,…

4. Most of the extractives are present at…

5. In general the vitamin content of white fish muscle is…

6. Vitamins can be divided into two groups,…

7. In white fish of the cod family, the fat content of the muscle…

Exercise 7. Fill in the blanks with prepositions for, of, to, in:

1. Two essential amino acids called lysine and methionine are generally found … high concentrations … fish proteins.

2. Reduction … a basic food resource, plankton … example, can affect the whole food chain.

3. The vitamin content … different parts … the same fish, can also vary considerably.

4. These extractives known as volatiles, contribute directly … the flavour and odour characteristic.

5. Free amino acids are not bound … the protein structure.

Exercise 8. Say if the sentences are true or false using the information from the text:

1. If spawning period is to be fully and economically utilized, amino acids must not only be present but must also occur in the correct proportions.

2. Unlike the proteins, extractives have comparatively large molecules.

3. The mineral and vitamin content of fish is greatly affected by careful processing or by preservation.

4. Measurement of the extractives amount can often reduce the storage time and hence indirectly the quality.

5. The term lipid is more correct, since it includes fats, oils and waxes as well as more complex, naturally-occurring compounds of fatty acids.

Exercise 9. Answer the following questions:

1. Why is it important to know chemical composition of fish for consumer?

2. Why is it important to know chemical composition of fish for producer?

3. How and when does it change?

4. What factors influence the chemical composition of fish?

5. What are the principal chemical components of fish?

6. What is the main constituent of fish flesh?

7. How does water and protein amount changes in spawning time?

8. What is the average amount of protein in fish muscle?

9. What two main amino acids are found in fish proteins?

10. What vitamins do fish contain?

11. What two groups are vitamins divided into?

12. What minerals are found in fish?

13. What other chemical components can be found in fish?

Exercise 10. Speak about a) factors affecting the composition of fish;

b) the principal components of fish muscle;