re reaching the
surface, because of the decrease in the water pressure.

One reason why fish are not numerous far out in the ocean is because
there is little food to be had there. The reason no fish are found in
the very deep parts of the ocean is because the water there contains no
air particles. Strange as it may seem, although fish breathe water, they
cannot live unless it contains oxygen from the air.

The fish, then, that interest us because of their value for food, are
found only in the shallow waters usually near the shore and in the lakes
and rivers. Because of this fact it is possible, as we have learned from
experience, to set so many traps and use so many nets and hooks as
entirely to destroy certain species.

The fish have their natural enemies, and there is warfare among them
just as there is among the land animals. The larger and more powerful
live upon the smaller ones, but, seemingly to make up for this, Nature
has given the small fish quickness of movement--which the large fish do
not possess--to aid them in escaping. They have also the power of
increasing very rapidly. The little herring, which is the chief food of
many of the large fish, maintains its countless numbers against all its
enemies except the fishermen.

The Indians, with their crude traps, hooks, and spears, could obtain but
few fish at a time and did not reduce their numbers. But civilized man,
with his cunningly contrived hooks and nets, has the same advantage over
the fish that the hunter, with his repeating gun, has over the land
animals. Nature, not foreseeing how destructive man would be, has armed
neither the creatures of the land nor the creatures of the water against
him.

The fisherman does his work just as thoughtlessly as the hunter whose
business it is to supply the market. He seems to think no more about
the effect upon next season's supply, of his stretching a net across a
river and catching all the fish going up to spawn, than does the market
hunter who would, if he could, shoot the last duck. Is it not strange
that many fishermen will do anything in their power to evade the laws
governing the catching of fish when by doing so they injure their own
business?

[Illustration: _Edward S. Curtis_
A rocky island in the Pacific Ocean, used by seals as a sunning place.]

We have already nearly destroyed the mammals that live in the ocean.
Among them are the whales, which were once numerous in the arctic
regions. Few w