Vocabulary

side сторона, бок, край, стенка, зд. стена compacted плотный, массивный, сжатый

slope уклон

ration соотношение, пропорция shallow плоский

management управление, умение справляться с чем-либо

to exceed drain inflow

to be in stock static

linear raceway to expose cage net-pen

превышать дренаж, осушение

втекающий, впадающий иметь в наличии статичный, неподвижный

узкий и длинный, подобный линии лоток, рыбоходный канал подвергать, зд. оставлять

садок, изолятор

садок, огороженное место сетями для

выращивания объектов марикультуры fry малек

extent степень withstand выдерживать

hatchery инкубаторная станция

Exercises

1. Choose the equivalents.

Sides slope; steeper slopes; to have a drain; to remove water completely; to fill a pond with water; to maintain higher densities of culture animals; a linear channel or a circular

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tank; raceways are used in hatcheries; to maintain densities up to …, to expose fish con-tinuously to the same water during the growing period; to exchange water completely; to place in a natural environment; cage culture is conducted in freshwater environments; net-pens are used in the marine environment; to withstand storms without damage. Держать рыбу постоянно в одной воде в период роста; наполнять пруд водой; выдерживать шторм без повреждений; ступенчатые уклоны; менять воду пол-ностью; садки применяют в морской среде; удалять воду полностью; помещать в естественную (природную) среду; узкий и длинный канал или круглый танк; поддерживать высокую плотность до ….; иметь дренаж; уклон стенок; лотки используют на инкубаторных станциях; в морской среде используют садки (се-тевые); в пресноводной среде используют садок (изолятор, клетку).

2. Answer the questions: 1. What is a typical pond?

2. What should a well designed pond have? 3. What are raceways?

4. What are raceways used for?

5. Is the water exchanged in raceways or not?

6. What is the difference between cages and net pens? 3. Summarize the text.

4. Translate into Russian using a dictionary.

MANAGEMENT OF CULTURE SYSTEM

Once the species for culture has been selected and the culture system has been con-structed and stocked, aquaculturists must address various management concerns. In terms of things that should be monitored by the aquaculturists, perhaps the most impor-tant water quality variables are temperature, dissolved oxygen and ammonia. Other va-riables can be important under certain circumstances, but the three mentioned generally provide a good indication of the performance of the animals in the culture system. Temperature:

Aquaculture species are all “cold-blooded” or poikilothermic. That means that their body temperatures are virtually the same as the temperature of the water that sur-rounds them. Basically, there are two primary types of culture species with respect to temperature: warm water species and cold water species. Carps, tilapia, channel cat-fish and freshwater shrimp are examples of warm water species. Trout, salmon and

American lobsters are examples of cold water species. The optimum temperature for warm-water species tends to be about 86⁰F (30⁰ С), while that for coldwater species is often 59⁰F (15⁰C). Some species of aquaculture interest, such as the yellow perch,

have temperature optima between the warm and coldwater species and are known as mid range species. Few mid-range species are currently being cultured.

When temperature changes dramatically, and in particular, when it moves out of the optimum range, aquaticanimals are placed under strees. It is at such times that disease resistance is lowered and problems often arise. Knowledge of the temperature re-

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quirements of the species under culture and of the temperature at any given time will not only provide the culturist with valuable information about how well the animals are growing and how much to feed them, it will help to establish the disease resis-tance status of the animals.

Dissolved Oxygen:

Oxygen enters water by dissolution from the atmosphere and through the release of that element by plants during photosynthesis. Animals with gills respire by absorbing oxygen that has been dissolved in water directly into the blood steam through diffu-sion as a general rule, if the water contains 5 parts per millon (ppm or mgll) of oxy-gen, it will support aquatic organisms. Some fish, such as tilapia, can survive at very low concentration of oxygen, while others, such as trout, are stressed if the concentra-tion falls below 5 ppm.

Daily changes in temperature are very small relative to the changes that can occur seasonally, particularly in temperature climates. Daily changes in dissolved oxygen, on the other hand, can be substantial. Dissolved oxygen begins to increase at about dawn, when photosynthetic production of oxygen by the plant community begins. As the sun rises, photosynthetic oxygen production increases with the increasing amount of light energy available. While both plants and animals respire continuously, the rate of oxygen production exceeds respiration and there is a net increase in the dissolved oxygen level. At dusk, when there is insufficient light for photosynthesis, the oxygen level begins to drop because of respiration demands, and the drop continues through the night. As long as the lowest morning dissolved oxygen level is not below about 5 ppm, there should be no problem. However, the lowest level of dissolved oxygen can change dramatically from one day to the next. Daily production of oxygen can be in-fluenced by the weather (cloudy days don’t support as much photosynthetic activity as clear days) and by the biomass of culture organisms present. As the fish or shell-fish being raised grow, they extract more oxygen from the pond each day.

Ammonia:

Ammonia occurs in two forms, unionized (NH3) and ionized (NH4). The ratio be-

tween the two depends on temperature, pH and a few other factors. Ammonia is ra-pidly converted to nitrate (N⁰³) by plants and bacteria in aquatic systems. Thus, in

ponds where there are plenty of plants and bacteria present ammonia toxicity is not usually a problem. In raceways and other water systems where animals are reared at high densities, ammonia removal is often not as efficient as in a pond, and toxicity can occur. Different species of aquaculture interest have different tolerances for am-monia. Tilapia can tolerate high concentrations of total ammonia (several ppm), whe-reas trout are highly susceptible to levels well below 1 ppm.

Word supplement:

poikilothermic- пойкилотермное животное (имеющее непостоянную температуру тела)

dissolution растворение, ражжижение

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respire bloodstream

unionozed ammonia (NH3) ionized ammonia (NH4) nitrate

дышать

кровообращение, кровоток аммиак

ионизированный аммиак 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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Once a diet has been formulated and the ingredients have been mixed together in the proper proportions, the material is usually made into a pellet. Pellets are made by ex-posing the material to high pressure in a pellet mill or extruder. Pellet mills may use steam to help bind the ingredients together. Extruders use supplemental heat and ex-tended exposure to high pressure to make pellets. Pressure pellet mills and extruders pass the feed mixture through a small aperture which leads to a product which, is not cut to short lengths, would be much like spaghetti strands. The diameter of the pellets varies, but is typically 0.2 to 0.24 inches ( 5 to 6 mm). A knife cuts off the strands as they exit the pelleting equipment. Feeds produced by pressure pelleting are more dense than water; thus, they sink. During the extrusion process, on the other hand, the high heat used causes changes within the ingredients so that starches expand when the pellets leave the machine and come into contact with air. This rapid expansion of the material traps air within the pellets, which float when placed in water. Because of the higher temperatures and other factors, extruded pellets are more expensive than pressure pellets. Advantages of floating pellets are that the aquaculturist can see that the fish eat feed. By watching the fish eat, the producer can control the amount of feed offered and thereby avoid overfeeding. This can save money. If the fish develop a disease, the aquaculturist may be able to identify the problem by observing changes in the behavior or appearance of the fish and can treat the problem before it progress very far. Floating feeds should not be used on all aquaculture species. Shrimp, for ex-ample, feed on the bottom and will not swim to the surface for pellets. However nu-trients will be quickly lost from sinking pellets which may dissolve in a few minutes (floating pellets may take 24 hours or more to disintegrate), so valuable sources of nutrition can be lost if the animals do not consume the feed quickly. Also, bacterial and fungal growth on feed particles that are not quickly consumed can lead to disease or toxicity problems.

Vocabulary

to rely on nourishment to feed on food chain

полагаться на питание питаться

пищевой симбиоз (совместное

проживание организмов с обоюдной пользой друг для друга)

macrophyte invertebrate (s)

to meet requirements crustacean cholesterol

to determine diet

with respect to

макрофит беспозвоночные отвечать требованиям ракообразные холестерол

устанавливать, определять пища

в отношении, что касается

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feed carbohydrate

poultry by product meal

корм углевод

пищевая добавка

для домашней птицы

wheat corn meal

peanut meal cottonseed meal true

to formulate pellet

to expose to to extrude steam

to bind supplemental extended exposure aperture strand

inch to exit to sink

to cause starch

to expand to trap

to float advantage to avoid

to disintegrate fungal

fungus

пшеница кукурузная мука

мука земляного ореха (арахиса) корм из хлопкового семя верный, правдивый, точный разрабатывать

гранула, шарик подвергать чему-либо

прессовать, штамповать, выдавливать пар

связывать, соединять дополнительный длительный подвергание отверстие, щель нить, волокно

дюйм выходить погружаться вызывать крахмал увеличиваться

зд. задерживать, сковывать держаться (плавать) на поверхности преимущество

избегать

распадаться, разрушаться грибковый

гриб, плесень

Exercises