Fish Farming

Fish farming is the principal form of aquaculture, while other methods may fall under mariculture. Fish farming involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish hatchery. The most important fish species raised by fish farms are, in order, salmon, carp, tilapia, catfish and cod.

Increasing demands on wild fisheries by commercial fishing has caused widespread overfishing. Fish farming offers an alternative solution to the increasing market demand for fish and fish protein.

There are two kinds of aquaculture: extensive aquaculture based on local photosynthetical production and intensive aquaculture, in which the fish are fed with external food supply. The management of these two kinds of aquaculture systems are completely different.

Limiting for growth here is the available food supply by natural sources, commonly zooplankton feeding on pelagic algae or benthic animals, such as crustaceans and mollusks. Tilapia species filter feed directly on phytoplankton, which makes higher production possible. The photosynthetical production can be increased by fertilizing the pond water with artificial fertilizer mixtures, such as potash, phosphorus, nitrogen and micro-elements. Because most fish are carnivorous, they occupy a higher place in the trophic chain and therefore only a tiny fraction of primary photosynthetic production (typically 1%) will be converted into harvest-able fish. As a result, without additional feeding the fish harvest will not exceed 200 kilograms of fish per hectare per year, equivalent to 1% of the gross photosynthetic production.

A second point of concern is the risk of algal blooms. When temperatures, nutrient supply and available sunlight are optimal for algal growth, algae multiply their biomass at an exponential rate, eventually leading to an exhaustion of available nutrients and a subsequent die-off. The decaying algal biomass will deplete the oxygen in the pond water because it blocks out the sun and pollutes it with organic and inorganic solutes (such as ammonium ions), which can (and frequently do) lead to massive loss of fish.

In order to tap all available food sources in the pond, the aquaculturist will choose fish species which occupy different places in the pond ecosystem, e.g., a filter algae feeder such as tilapia, a benthic feeder such as carp or catfish and a zooplankton feeder (various carps) or submerged weeds feeder such as grass carp.

Despite these limitations significant fish farming industries use these methods. In the Czech Republic thousands of natural and semi-natural ponds are harvested each year for trout and carp. The large ponds around Trebon were built from around 1650 and are still in use.

НУБіП України Ф-7.5-2.1.6-24

НАЦІОНАЛЬНИЙ УНІВЕРСИТЕТ БІОРЕСУРСІВ ТА ПРИРОДОКОРИСТУВАННЯ УКРАЇНИ

Факультет Педагогічний

Напрям підготовки Філологія (переклад)

Форма навчання денна

Семестр 4-6 Курс4

ОКР «Бакалавр»

Кафедра романо-германських мов і перекладу

Дисципліна Практика письмового та усного перекладу

Викладач Сидорук Г.І.

«Затверджую»

Завідувач кафедри (Ніколенко А. Г.)

«»2012 р.

Maize

Maize (also known in most English-speaking countries as corn), is a grass domesticated by indigenous peoples in Mesoamerica in prehistoric times. Native Americans cultivated it in numerous varieties throughout the Americas. The Mississippian culture, whose major city and regional chiefdom of Cahokia in present-day Illinois achieved its peak about 1250 CE, had population density and a great regional trade network based on surplus maize crops. As another example, the women of the Pawnee nation on the Great Plains were known to cultivate ten pure varieties of corn by the late 18th century. After European contact with the Americas in the late 15th and early 16th centuries, explorers and traders carried maize back to Europe and introduced it to other countries through trade. Its use spread to the rest of the world.

Maize is the most widely grown crop in the Americas (332 million metric tons annually in the United States alone). Hybrid maize, because of its high-grain yield as a result of heterosis ('hybrid vigor'), is preferred by farmers over conventional varieties. While some maize varieties grow up to 7 metres (23 ft) tall, most commercially grown maize has been bred for a standardized height of 2.5 metres (8.2 ft). Sweet corn is usually shorter than field-corn varieties.

The term maize derives from the Spanish form of the indigenous Taino word maiz for the plant. This was the term used in the United Kingdom and Ireland, where it is now usually called "sweet corn", the most common form of the plant known to people there.

Outside the British Isles, another common term for maize is "corn". This was originally the English term for any cereal crop. In North America, its meaning has been restricted since the 19th century to maize, as it was shortened from "Indian corn." The term Indian corn now refers specifically to multi-colored "field corn" (flint corn) cultivars.

In scientific and formal usage, "maize" is normally used in a global context. Equally, in bulk-trading contexts, "corn" is used most frequently. In the UK, Australia and other English-speaking countries, the word "corn" is often used in culinary contexts, particularly in naming products such as popcorn and corn flakes. "Maize" is used in agricultural and scientific references.

Maize stems superficially resemble bamboo canes and the internodes can reach 20–30 centimetres (8–12 in). Maize has a distinct growth form; the lower leaves being like broad flags, 50–100 centimetres long and 5–10 centimetres wide (2–4 ft by 2–4 in); the stems are erect, conventionally 2–3 metres (7–10 ft) in height, with many nodes, casting off flag-leaves at every node. Under these leaves and close to the stem grow the ears. They grow about 3 millimetres a day.

The ears are female inflorescences, tightly covered over by several layers of leaves, and so closed-in by them to the stem that they do not show themselves easily until the emergence of the pale yellow silks from the leaf whorl at the end of the ear. The silks are elongated stigmas that look like tufts of hair, at first green, and later red or yellow. Plantings for silage are even denser, and achieve a lower percentage of ears and more plant matter. Certain varieties of maize have been bred to produce many additional developed ears. These are the source of the "baby corn" used as a vegetable in Asian cuisine.