Friday, 30 December 2011

How Fish Sleep

How Fish Sleep
By A. Hyatt Verrill
From Everyland magazine, Everyland Nature Club column, Oct. 1916, digitized by Doug Frizzle, Dec. 2011.

DOESN'T it seem funny to think of fish going fast asleep? Most people think of fish as always being wide awake and swimming about, but, strange as it seems, fish sleep just like other animals, and some of them even make beds in which to sleep.
Still other kinds sleep upon the surface of the water and rest just as comfortably, when tossing about on the-waves, as their cousins resting in their beds on the bottom.
Some kinds of fish change their clothes before going to bed and put on night-dresses which are so very different from their everyday clothes that you would never recognize them, while others never bother about such matters, but doze off wherever they happen to be when sleepy.
But the funniest thing about fish sleeping is that they never shut their eyes, for fish do not have eyelids like most animals, and so they couldn't close their eyes if they wanted to. For this reason fish are all very light sleepers, and wake up at the least change of light, or at a shadow moving past them. This is why it is so hard to catch a fish asleep, for even in an aquarium the finny creatures wake up as soon as any one goes near.
Some fish sleep much more soundly than others, however, and nearly all we know about sleeping fish has been learned by watching these heavy-sleeping species.
I said some fish made beds, and any boy or girl who lives near a fresh water pond or stream in the United States may find some of these with a little search. The common "pumpkin seed," or "sunfish," is a fellow who makes these beds, which look like little hollows lined with sticks and pebbles upon the bottom of the pond or stream. If you approach very cautiously you may be able to find one of the fish resting in its "nest," and fast asleep, for fish doze in the daytime as well as at night. Another kind of fish, also known as the "sunfish," is a great giant of a fish found in the open ocean, and this sunfish is one of the kinds which love to sleep on top of the sea. This funny sunfish, which looks as if he were all head, is one of the largest of all fish, and when he sleeps he lies in a nice comfortable position with his big fin sticking up in the air. This big sunfish is a very sound sleeper, and sometimes one may be seen with half a dozen seabirds perched on his fin while he slumbers on without knowing he is the resting place of his feathered friends.
But the funniest fish are those which wear nightclothes. One of these is the common "blackfish," or "tautog," and as the blackfish are very sound sleepers, one may watch them very easily when they are kept in an aquarium. During the day the blackfish is dull colored, dark brown or nearly black, with faint blotches or stripes, but when he goes to bed he changes his colors and sleeps in a suit of silver and black. Like many other fish, the blackfish rests on the bottom, and lies on one side, or propped up against some rock or weed. If you should see a blackfish sleeping in this way you would certainly laugh, for, resting on his side with his mouth half open, he looks as if he were actually snoring.
Illustrations by the Author
Another common fish who puts on a night-dress is the "scup" or "porgy." During the day the scup is plain silvery gray, but when he feels sleepy he puts on a coat of brown and gray stripes. Then he searches about until he finds a nice comfortable spot among the eel grass or seaweeds where he goes to bed and sleeps soundly, for he knows the striped nightgown will make it very difficult for any enemy to see him among the shadows of the weeds. It is for this very reason that the sleeping fish change their colors, for if dressed in their daytime clothes some prowling shark or other foe might come along and gobble them up before they were half awake. This is known as "protective coloration," and while the commonest fish—such as the blackfish and scup, protect themselves in this way, yet some of their cousins are much more remarkable in their manner of changing color to protect themselves while asleep.
One of the commonest and most wonderful of these is the green parrot-fish, found along the southern coasts of the United States and in tropical waters.
During the day and when awake, the parrot-fish is a beautiful clear turquoise green, but just as soon as he goes to the bottom to rest or to sleep, his colors change to a dull olive covered with spots and blotches of brown. In this costume you would never recognize him. But the funniest part of it is that he knows when to change his coat and when not to, and if he is placed in an aquarium with a plain green bottom he will go to sleep in a coat of plain green. Then, if some stones or other objects are placed in the aquarium he will make the brown spots appear on his body, and unless you look very closely you will find it impossible to distinguish the wise little fish as he snuggles down among the pebbles in his piebald suit.

No comments:

Blog Archive

Countries we have visited

About Me

My photo

As an armed forces brat, we lived in Rockcliff (Ottawa), Namao (Edmonton), Southport (Portage La Prairie), Manitoba, and Dad retired to St. Margaret's Bay, NS.
Working with the Federal Govenment for 25 years, Canadian Hydrographic Service, mostly. Now married to Gail Kelly, with two grown children, Luke and Denyse. Retired to my woodlot at Stillwater Lake, NS, on the rainy days I study the life and work of A. Hyatt Verrill 1871-1954.