LESSON XLII.
WHERE THEY LIVE.
Where does the fin family live? “In the water,” you say. Yes. There is perhaps no natural body of water in the world without its fish. There are forty families of fresh-water fish. There are fish that live in water that is partly salt and partly fresh, as where the sea-tides run back into rivers. There are fish that live in the salt water of the ocean.
IN FRESH WATER.
IN FRESH WATER.
The ocean fish are divided into three classes. First there are the coast fish, that seldom go far from shore. They need a certain kind of food and a certain warmth of water that they find near land. Then there are surface, or upper-sea fish, that live far from land, but never very deep in the water. And there are the fish of the very deep sea.
The surface, or upper-sea fish, are most of them very strong swimmers. The deep-sea fish live far down where there is little air and almost no light. It is only about twenty years since people began to study deep-sea fish, and as yet little is known about them.
Many of the shore, or coast fish, that live in sea-water, enter the rivers to lay their eggs. They arrive in the rivers in the spring, and sometimes go up even hundreds of miles from the mouth to find safe places for their young. Thus these fish are born in fresh water, and grow up in salt water.
Among fish of this habit, we find the shad and the salmon. So you see a fish may live part of its time in salt water, part of the time in fresh, and part of the time in the brackish water at the river’s mouth. Some fish, that are accustomed to spend all their lives in sea-water, can be made to live in fresh water, if this is changed gradually.
When fish live in a tank, air must be driven into the water to supply what the fish use out of it. If air is not driven in, the fish will die. As the oxygen in the water becomes scarce, the fish seem uneasy. They come up to the top of the water, and put their mouths out for air. They give a gasp as if choking.
In such tanks, where fish live, a jet of water is driven with some force into the water of the tank from above. As it goes down, you see a stream of shining bubbles. These bubbles are air. They break in the water, and the air mingles with the water in the tank.
You may see gold-fish in globes coming to the top of the water, and seeming uneasy and unhappy. Then if you dash in a little fresh water, or take some of the water from the globe and pour it back from a little height, the fish seem content.
You know that the driving winds and the tumbling waves that break in foam will keep plenty of fresh air in ocean water, for all the finny tribes that live there.
So rivers, as they rush and ripple, toss their waves, and are driven with winds, get air bubbles mixed in their waters.
Some fish need more air than others, and often cometo the surface to breathe. Some, as the sturgeon, leap above the surface into the air. Perhaps you have seen cat-fish jumping in this way. Did you ever see dolphins and porpoises[31]roll themselves quite above the surface of the water in their play? I have told you of the fish that make short flights. In all these ways these creatures help themselves to air in their water home. But what do they do for food?
As I told you, fish eat fish and insects and crabs and such living things. Some few are feeders on vegetables. Fish will also devour almost anything that is thrown into the water for them. Did you ever feed fish in a pond with bread and worms?
Carp will hurry to the top of the water to get food that they have learned to look for when people come near. Fish of a kind often keep together and feed together. You know in a stream there may be some places where you will catch only trout, or only bullheads. And in some other place you will find pickerel.
In the sea you will find millions of herring together at certain seasons. This is called a shoal of herring.Fish move from place to place along many miles of sea-coast or river, as they seek their especial food, or a certain warmth.
Sometimes a particular fish, or pair of fishes, will live for years in some certain place. They may find a nice spot under a bank, where they feel safe, and where plenty of food drifts near them.
I knew of a fish that went into a hole made by the roots of a great willow-tree. The roots formed a close cage about him. He liked it well. His enemies could not get at him. Water rippled in and out about him. Grubs and worms were close to his mouth. He grew fat and big. He grew so big he could not get out. He began to grow to fit the shape of his cage. As he had no room to grow long, he grew broad.
After some years he was a very queer-looking fish. Finally, some men were making an embankment, and they came upon this fish-home in the roots of the tree. They took the fish out with care, and sent him to a pond. I fancy it seemed odd to him to swim at first, after being so long a prisoner.
There are some kinds of fish that live and thrive in the icy-cold waters of polar seas. There are other fish that live in hot springs or ponds, where the water is so hot that you can hardly bear your hand in it.
Some fish can live only in very clean water. Others live in black and muddy streams, and their flesh takes the dark hue of their home. In fact, there seem to be some kinds of fish made to suit every kind of water. This is very fortunate, as so many birds and beasts and so many people eat fish.
FOOTNOTES:[31]The dolphin of the Mediterranean is of the whale family, and is not a true fish. The dolphin of the Atlantic is a true fish. The porpoise is of the whale family, not a true fish, but a mammal.
[31]The dolphin of the Mediterranean is of the whale family, and is not a true fish. The dolphin of the Atlantic is a true fish. The porpoise is of the whale family, not a true fish, but a mammal.
[31]The dolphin of the Mediterranean is of the whale family, and is not a true fish. The dolphin of the Atlantic is a true fish. The porpoise is of the whale family, not a true fish, but a mammal.