Childrens Illustrated Encyclopedia

389

LIFE BEGAN IN THE OCEANS millions of years ago.

Today, oceans cover 71 percent of the planet’s surface

and provide homes for countless fish, octopuses, seals, sharks, and

jellyfish. Ocean wildlife is at its richest in the warm shallow

waters of coral reefs, where dazzlingly colorful angelfish and

butterfly fish live. In deeper waters, whales, dolphins, and

porpoises are found. Most plants and animals live close

to the water’s surface. Sunlight filters through the

surface, allowing microscopic organisms, such as

diatoms, to flourish. An intricate web of small

animals feeds on these tiny organisms; larger

sea creatures eat the smaller ones, and so on up

the food chain to the large predators such as sharks.

Today, many marine plants and animals are

threatened; we dump chemical wastes in the oceans,

fertilizers flow into the oceans from rivers, and we

catch so many fish that fish-eating sea

mammals such as seals and dolphins

have to compete with us for their food.

PLANkTON

Billions of tiny organisms float

in seawater. Together they are

called plankton, from the

Greek word planktos, meaning

“wanderer.” Plankton are food

for many fish and other

sea creatures.

FINBACk wHALE

The finback whale is the second

largest living animal (the blue

whale is the largest) and is

found from the poles to

the tropics. Finbacks

grow to about 85 ft (25 m)

in length and weigh 71 tons. They feed by

straining shrimplike creatures called krill

from the water, using fringes of baleen

hanging from the upper jaws.

HErrING

There were once vast schools

of herring in the oceans; they

were an easy catch for fishing

boats, and people valued them

for their tasty flesh. Today, herring

is much less common because people

have overfished the oceans. Herring

feed on plankton.

Common squid

SANd TIGEr

Sharks are the most aggressive

hunters in the ocean. The ferocious

sand tiger shark hunts even before it

is born, when it is still in its mother’s

womb. There are 10–15 embryo sharks

in the womb, and as they develop, they

eat each other until there are only one

or two left. The survivors are born fully

formed, then swim away to begin their

fish-eating lives, growing to 12 ft

(3.5 m) in length.

Finback whale

OPEN OCEAN

Many animals in the open sea are

streamlined (sleek in shape) so that they

can swim away quickly from predators and

chase after prey. There are fish of all

shapes and sizes in the open ocean, as

well as enormous schools of jellyfish

and mammals, such as seals. Sea

birds, such as albatrosses, petrels,

and shearwaters, feed at

the surface.

Ocean wildlife

SArdINE

Pacific sardines

are related to

herrings. Other

members of the

herring family are the sprat

and the shad. All of them are hunted

by bigger ocean dwellers such as seals.

SwOrdFISH

This spear-nosed hunter is one of the fastest fish in the sea; it can swim

in bursts at speeds of 60 mph (95 km/h). The swordfish resembles the

marlin and sailfish, and weighs up to 1,500 lb (675 kg).

Swordfish injure their prey with sideways slashes of

Swordfish the sword, and then devour them.

Sea birds

COELACANTH

The coelacanth is a survivor from

prehistoric times, although scientists

first discovered it in 1938. The

coelacanth lives around the Comoro

Islands, off southeast Africa, and in

the eastern Indian Ocean, in water

230–1,300 ft (70–400 m) deep. Adult

coelacanths measure about 5.5 ft (1.7 m)

in length. Today, this fish is threatened

because of fish collectors and

souvenir hunters.

US_389_Ocean_Wildlife_1.indd 389 09/02/16 3:57 pm