My Science School

The natives of South America are terrified of the piranha fish, a fierce creature that resemble the tiger in its voracity. Piranha fish, which live in the rivers of South America, especially in the region of the Amazon and the Orinoco, can be included among the fiercest animals of the world.

Piranha fish are less than 40 centimetres long but they have massive jaws and strong razorsharp teeth which are like a very sharp saw and cam tear through even the toughest leather. The piranha’s teeth are triangular in shape and fit exactly into one another; with such teeth these fish can tear even large animals to piece.

Cattle are frequent victims of the piranha fish whenever they try to cross a river, but these fish will also attack human beings. When herdsmen want to take a herd of cattle across a river they select the worst beast and throw it into the water first. Attracted by the blood the piranha fish devour the animal while the rest of the herd is taken safely across the river.

 

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Only a few fish can adapt to life in the restricted space of a tank, but even these will die if they are not given the right surroundings.

The aquarium must be carefully prepared. On the bottom there should be a mixture of sand and pebbles to give a realistic look. Underwater plants are useful because they help to keep the water pure by absorbing waste products and providing oxygen. The water must be neither too cold nor too warm and it must not contain any harmful substances. It should cover to the aquarium is often used, to reduce evaporation and prevent the fish from jumping out.

 

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Goldfish make extremely popular pets. They are not difficult to look after providing you follow a few simple rules.

The first serious threat to a goldfish is when it is taken home from the pet shop. It should be swimming around in quite a lot of water and you should not take it in one of those small plastic bags. If you must use a plastic bag take the goldfish out of it as soon as possible or it may suffocate.

A second danger to goldfish is the tank it swims in. Tap-water contains chlorine which is poisonous to goldfish. This water is also too cold and might kill the pet.

A third danger is feeding which is all too often wrong for goldfish. These fish do not require much food, but what they do eat must be carefully chosen. Never give goldfish breadcrumbs: use the special food sold in shops but be careful to give it only in small quantities. Occasionally you can give goldfish a small amount of finely minced raw meat or the crushed yolks of hard-boiled eggs.

The larger the tank the happier the fish will be. The ideal tank is the aquarium but a large bowl will serve. Do not forget that even a goldfish can become bored and pine away living alone, so you should give it a companion, either male or female. Goldfish were originally natives of eastern Asia but were later introduced into China, Japan, Europe and the United States. They have been known to live for twenty-five years in captivity, but the average life span is usually much shorter.

 

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There are certain fish which present serious dangers even to man because of their strength and ferocity. The shark is an obvious example, but among the most dangerous are the poisonous fish which use their venom in a number of ways.

Some have their flesh completely impregnated in poison and any attacker who bites them or eats them will die. Other fish impregnate their eggs with poison to protect their unborn young.

There are also fish with spines of fins that contain poison and others with teeth that carry venom, just like snakes. The most unusual weapon belongs to the stingray. This is a strange, flat fish that spends much of its time on sandy or muddy bottoms of shallow waters where it is almost invisible. Most stingrays inhabits warm seas, but a few kinds are founds in the rivers of South America.

If the fish is trodden on it lifts its tail which contains a sting can inflict serious wounds, especially when the long, thin tail is lashed. The poison is painful; it can paralyze and, in some cases, prove fatal.

 

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Fishing is one of the oldest activities known to man. Early man who lived on houses erected on poles above the water of lakes, soon learned how to catch the silent creatures that swam around underneath the surrounding waters. The fishing methods of those primitive peoples did not differ much from the lines, nets and hooks of today.

The implements used in fishing can be quite complicated, such as the lobster pots that are sunk, laden with bait, to the sea-bed and the nets which are rigged up by groups of people working together. When these nets are dragged along the water they are known as trawls.

Other types of nets are placed in the water to form a ring which is then gradually closed round the fish and lifted out of the water. This method is known as purse seining. In other netting systems fishermen simply block the fish’s means of escape and force them to swim into a special area where they are caught.

 

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