Hello everyone,
Today we're talking about Atlantic salmon.
Atlantic salmon are found in the north Atlantic and the rivers that flow into
it. They can grow up to a meter long and are classified as
Least Concern
by the
IUCN.
Atlantic salmon start their lives in rivers. The pea-sized eggs are laid in
autumn and hatch in April or May. The tiny salmon are called alevins. They
feed on aquatic invertabrates and eventually devolop into parr. Parr are
easily recognised by destinictive patterns and markings on their flanks.
After up to several years, the parr develop a silvery sheen. These replace
those characteristic parr markings. Their bodies change in preparation for the
salt water and they are now called smolts. They swim downstream with the
current all the way to the ocean. In the deep sea waters, the smolts feed on
crustaceans and small fish for 15-50 months. However they are hunted by a
number of predators including, sharks, seals and of course humans. Their
numbers reduce significantly and only 10% of the smolts survive.
They then return to the same river where they themselves were born. It isn't
proven how they locate the exact river but theories include using the Earth's
magnetic field, using knowledge of ocean currents and having a chemical memory
from when they left. In the estuaries, they turn into tartans. The females
become darker and have multi-coloured patterns on their flanks. Males develop
red bellies and streaky flanks. The tartans make their way up the river. When
they come across a waterfall or other obstacle, they simply jump over it. This
is known as the salmon leap and can be observed in autumn. The salmon can jump
over 3m by using powerful muscles in their tails.
After making it up the river, they lay and fertilise their eggs in a shallow
strech of river. This uses up so much energy that 90% of the adults that made
it up the river, die after the eggs have been laid and fertilised. The
survivors, known as kelts, return to the ocean and may repeat the process a
few years later.
We hope you enjoyed this post and found it interesting. If you're in a part of
the world that has Atlantic salmon, look out for the salmon leap in autumn.
It's escpecially spectacular after lots of rain.
Your Green World Blog Team💚
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