Page 62 - Engineering in Nature
P. 62
Engineering in Nature
The above picture shows the developmental stages that salmon undergo from birth
until they complete their migrations.
several weeks, those who survive to reach the open sea thus complete
their first migration and finally reach their objective, the Pacific
Ocean. After spending a few years in the sea, those which grow to full
maturity embark on another, really astonishing, migration.
As the salmon swim down the river, a number of physiological
changes take place. From being creatures that live in fresh water they
adapt to the salt waters of the sea. After spending a while at the
mouth of the river in order to acclimatize themselves to salt water,
they move to the ocean where they will spend most of their adult
lives. When the fish return to the rivers to lay their eggs, this process
18
is reversed.
• The Salmon's Difficult Journey Begins
The salmon now begin swimming against the current, up the same
60
