Page 172 - The Miracle of Migration in Animals

THE MIRACLE OF MIGRATION IN ANIMALS

The Upstream Migration of Salmon

Having to swim in the salt ocean, swimming upriver, sometimes
leaping over waterfalls 3 meters (10 feet) tall without crashing into
rocks—these are only a few of the trials that migrating salmon un-
dergo in order to spawn.
The most important characteristic of salmon, which spawn in
rivers along the western coasts of North America, is their ability to
cross rivers and even jump waterfalls in the course of their migration
journey. In breeding season, the females lay their eggs in a shallow
stream. The young feed on nutrition already in the yolk sac attached
to them. After a few weeks, they are ready to search for food in the
stream, where they live for about a year.
At the same time, thousands of salmon start migrating along the
riverbed. Their final destination in a journey that lasts some weeks is
the Pacific Ocean.
Salmon’s physical constitution enables them to live in both fresh
and salt water. As soon as they reach the ocean, a structural change
takes place in their bodies that prepares them for saltwater life. In the
ocean for the next one to four years, they will cover great distances,
until they have matured and are ready for the final and most
difficult journey of their lives. They are ready to return
home, to the fresh running water where they were
spawned.
Now they start swimming upriver against the flow in the same
riverbed they once descended down to get to the sea. No obstacle
they encounter defeats them. Even when faced with waterfalls, they
continue on their way leaping up through tons of flowing water. They
can even leap over 3 m (10 feet) obstacles. Indifferent to any wounds
on their bodies, they continue on their way. And finally they reach the

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