Английский язык: Сборник текстов и упражнений для студентов специальностей "Промышленное рыболовство". Дьякова Н.П. - 59 стр.

      respire                                    дышать
      bloodstream                                кровообращение, кровоток
      unionozed ammonia (NH3)                    аммиак
      ionized ammonia (NH4)                      ионизированный аммиак
      nitrate                                    нитрат

                                    TEXT 21
                             NUTRITION AND FEEDING

Under natural conditions in ponds, lakes, rivers and the ocean, fishes rely on natural
productivity for their nourishment. Some aquaculturists also use natural food organisms
to provide nourishment for the culture species. In China, for example, ponds are stocked
with various species of carp that feed on different parts of the food chain. The fish ponds
may be fertilized to help promote growth of phytoplankton, rooplankton, rooted aquatic
macrophytes and benthic organisms, each of which is fed upon by a different type of
carp. In Japan and a few other countries, ground raw fish is often used to feed aquacul-
tured animals (the fish may be fixed with small) amounts of dry ingredients).
Oysters, mussels and clams are among the various shellfish that feed by algae and
other organic nutrients from the water. The culture of those animals requires the pres-
ence of large algae concentrations.
Most fishes and invertebrates of aquaculture interest are fed prepared feeds. Such feeds
are composed of various ingredients in proper combinations so that the final product
will meet the nutritional requirements of the species being fed. Diets vary considerably
from one type of aquaculture animal to the next because of differences in nutritional
requirements. For example, many crustaceans are unable to synthesize cholesterol, so
that chemical must be provided in the feed. Fishes, on the other hand, do not require
dictory cholesterol. Determining the nutritional requirements of an aquaculture species
can require many years of research. Diets are prepared in which various ingredients are
varied with respect to quality and quantity. Then the feeds are presented to the aquacul-
ture species over a period of several weeks to months and the growth response is eva-
luated. Experimental diets may be prepared to examine the responses of the animals to
variations in dietary protein, fat, carbohydrate, minerals, vitamins or energy. Typical
aquaculture diets are relatively simple. They usually contain some type of animal pro-
tein (fish meal, poultry by product meal, meat and bone meal) and other proteins sup-
plied by plants (soy bean meal, wheat, corn meal, peanut meal and cottonseed meal).
The plant products also supply high levels of carbohydrates (sugars and starches).
Some species, such as channel catfish, can tolerate levels of 40% carbohydrate in the
diet, whereas others, such as trout, tolerate only low carbohydrate levels. Fat is sup-
plied by the various ingredients mentioned, but supplemental fat is offen added in the
form of corn oil, fish oil or a variety of others. A mixture of required vitamins and
minerals is also usually added. In some instances, wet, ground fish is used in the Unit-
ed States as a dietary ingredient. This is particularly true in the Pacific Northwest,
where waste products from fish processing plants are readily available.

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