Fish : An Essay

When we say the word 'fish', the first image that comes to the mind is that of a slanting, streamlined colourful creature sliding in water, flapping its fins up and down, and jumping out of water when we throw food to it. But thinking this way is a very limited way of looking at a fish.

 The word 'fish' can be sometimes a tricky grammatical term for students because the same word stands for the plural too, but you should know that when we refer to different kinds of fish, we can very well use the word 'fishes', but for the same kind, the plural to be used remains the same 'fish'. So, you know the exact meaning when we use 'fish' or 'fishes' in the plural sense. The funniest thing about the word 'fish' is that all animals that carry it in their names are not necessarily fish; for example, jellyfish, crayfish, cuttlefish and starfish are not fishes.

Fish plays such an important part in our life that it has intruded our everyday language. We have a number of idioms and phrases that hinge on the word 'fish'. When you say that a person is like 'a fish out of water', you mean that she feels awkward or uncomfortable because she is not in familiar surroundings. When you say that you 'have bigger fish to fry', you mean that you have more important things to do. 'An odd fish' is a person who is slightly strange or crazy; and 'a big fish' is an important person. And when somebody points out that 'there are plenty more fish in the sea', he means that there are many other people or things that are as good as the one somebody has failed to get.

Fishes mean different things to different people. To many people, fishes are best known sources of food; they form a large part of food in the entire world, especially in the areas close to the seashores and water bodies. This has made catching fish an important source of livelihood for a very large number of people. To some people, fish are a source of sport or game, as they go out hunting them. Angling fish has been described to be an ideal pastime by many people, and may be, nobody seems to be talking about animal rights when it comes to fish.

Fishes are inhabitants of water, this fact is known to all people, but all those that live in water are not necessarily fishes, though they all coexist in water bodies including rivers, lakes and seas.

A true fish is a red-blooded, vertebrate animal which lives throughout its life in water. Its body is typically covered with scales. It breathes by means of gills. It propels itself by the sinuous movement of its body, aided by fins, which are the balancing organs. Most fishes breathe dissolved oxygen in water that bathes their gills; but a few like the lung-fishes have developed lung-like structures, which enable them to take in oxygen from the atmospheric air. Some of the lung-fishes are Epiceratodus, Protopterus and Lepidosiren.

A vertebrate is an animal with a backbone; a series of bones that we too have. Other than humans (who are mammals) and fishes, the other animals to have backbones are amphibians, reptiles, birds and mammals.

The largest fishes living today are sharks; they are found in abundance in the tropical and sub-tropical zones of the world. Indian seas are rich in sharks. Interestingly, whales look like a fish, but are not one, they are mammals in fact.

Thus, we see that fishes are of so many types and are so universally found in seas, rivers and lakes that they have been divided into several types of groups. Though they all look alike so far as the shape of their body is concerned, but different features of their bodies and organs have caused their classification into different groups. It is estimated that there are about 25,000 species of fishes living today. They are second to insects in the largeness of population, and they outnumber all other vertebrates, mammals, birds, reptiles and amphibians put together.

Fishes have had a long history. They first emerged about 430 million years ago. During this vast stretch of time, they have become adapted to all conceivable aquatic environments. They are the most common forms in rivers, rivulets, lakes and estuaries. They roam the open seas and have descended into the dark depths of oceans. They have climbed the rapid torrents of the mountains and crept into the crevices of cave waters. The story of their evolution is fascinating.

Fishes are curious to look because of their smooth body with scales, without legs and feet. And one of the most conspicuous features in fishes is the absence of the external ear, but they very well have the internal ear which is fully developed. They can very well recognize the sound produced by their own kind and can register sound waves conducted through water more sharply than through the air; this fact has been demonstrated by biologists through experiments. Fishes can also smell; their olfactory organs are paired, simple cup-like organs, which have no connection with the mouth. Most fishes have a high sense of smell, which enables them to detect their prey from a distance. Experiments on blinded sharks have shown that they can locate food with the help of smell alone. Salmon is a kind of fish that has an uncanny sense of smell. Fishes practically have no tongue, but they do taste through the oral membrane.

Fishes have a highly developed sense of touch, which most of them feel through barbels.

Have you seen a fire-fly, also called glow-worm or jugnu? It is abundantly found in our country. What makes it fascinating is the light that it emits in the dark. Among sea-creatures too, there are some that emit light; this phenomenon is called bioluminescence. It is in fishes that this process has reached its perfection. The great majority of deep-sea fishes living at depths of 90-550 metres or more have evolved light-producing organs, called photophores, which are varied in kind, number and origin. Deep-sea sharks produce greenish light.

What can be the use of these lighting organs in fishes? It is a biochemical process. The most obvious use is to provide light in places of darkness as in the deep seas, where sunlight does not penetrate. They are also used as defensive organs to confuse the enemy, as in lantern fishes. A further use may be as recognition marks for individuals of the same species, like spots and stripes. They also act as lures for prey as in wide-mouth fishes.

Some fishes have venom too, so it is not advisable to take every fish as food. Generally, fishes do not use their stings as organs of offence; they use them only on provocation, when attacked or stepped upon. In most cases, their venom is not life-threatening and can cause nausea, vomiting, diarrhoea, itching and numbness, sometimes accompanied by fall in blood pressure and heart rate.

Earlier it was thought that there are no separate males and females among fishes, so a large number of myths and legends grew around them. Some people said that they reproduced by spontaneous generation, while others believed that the young ones arose from the mucus or slime of their parents. But the truth is that there are males and females among fishes, and they come together to lay eggs. A fish can lay a very large number of eggs; for example, a cod, salmon or plaice may lay anywhere from 250,000 to 500,000 eggs in a single spawning season. You can see fish eggs during the rainy season in the local pond if there is one in the vicinity.