Shark, or other large
fish-hunter, merely has to rush into their ranks with wide-open mouth.
Hordes of Dog-fish feast on the edges of the shoal. And Gannets,
Cormorants, Gulls and other sea-birds can take their fill with ease.

The Herring shoal is a banquet at which the fish-eating sea creatures
feed heartily, and man comes along, to spread his nets in the path of
the shoal. But what matter a few million Herrings when the sea is packed
with billions more! In the North Sea, one shoal was seen which was over
four miles long and two miles wide. In such a mass there would be, at
the very least, twenty thousand million Herring; and this shoal was but
one out of many thousand shoals. One might as well try to count the
grains of sand on the shore as the Herrings in the wide ocean.

These huge shoals do not stay long in one part of the sea. They make
journeys of many miles, each shoal seeming to keep to itself. Like every
other creature, the Herring goes where his food is. What food does he
find? He swallows the small life of the sea, tiny transparent things
like baby shrimps, prawns, crabs, and so on, which swarm even in the
cold water which the Herring loves.

They are good juicy food, these little mites, and very plentiful; so no
wonder the Herring becomes plump. He eats greedily of this good food.
For instance, a young Herring, picked up on the beach at Yarmouth, was
found to contain no less than one hundred and forty-three small shrimps.
Not a bad dinner for a fish the length of this page! The ocean teems
with small creatures; even the huge Greenland Whale feeds on them, and
the Herring seems to live on little else.

Well, the shoals of Herring begin to move from their feeding place in
the deeps, and come nearer the coast. As they get to shallower water
they are crowded together near the surface. Where are they going, and
why?

Perhaps you can guess--they seek warmer, shallower water, in which to
lay their eggs. Now is the time for the fisherman! If the Herring kept
to the deep they would be quite safe--and we should have no nice plump
Herrings on our breakfast tables! Yes, now is the time to spread out
miles of nets in the path of this living mass of silvery fish. They are
in fine condition, well fed, and ready to lay their eggs.

They are moving slowly but surely towards the right place where those
eggs should be laid. What guides them? Why do they go _this_ way and not
_that_ in the vast ocean? We do not really k