Is this video bonkers, brilliant or both? Although the video
might be strange, the science is spot on.
The salmon journey from the sea to freshwater is unusual, epic
and fraught with danger.
Salmon spend their adult life in the sea. When they are ready to
breed, salmon can travel up to an amazing 1000 miles to fresh
water.That's like us walking from Paris to John O'Groats!
Fresh water is where salmon reproduce. In a stream or pond high
in oxygen, the female salmon digs a nest with her tail. She pushes
thousands of eggs into the nest for the chosen male to fertilise.
Then, most salmon die.
Young salmon, or alevins, hatch after around
one month. Alevins are tiny with huge eyes and attached to bright
orange food sacs, which are a bit like egg yolks. They hide in the
nest, under the surface of the stream bed, until they are bigger
and stronger.
Young salmon emerging from
stream bed. Photo by U.S. Fish
and Wildlife Service - Northeast Region.
After a few months, the young salmon - known as fry - emerge
from nest and feed on small insects. The young salmon stay for
several years in fresh water, feeding and growing stronger.
When they are strong enough, the teenagers of the salmon world -
known as smolts - swim downstream to salt water. This is a
dangerous trip. Lots of predators are out to get the salmon!
At the estuary, where the river meets the sea, the salmon
undergo smoltification. This is a complex internal
change that allows their bodies to adapt to salt water. If this
didn't happen, the salmon would become dehydrated and die in salt
water.
Atlantic salmon pre-smolt
stage. Photo by U.S. Fish
and Wildlife Service - Northeast Region.
The salmon live in the sea until they mature - between 1 and 7
years, depending on the species. When they are ready to breed, they
return to where they hatched. No one knows how salmon return home.
Perhaps they use their sense of smell. Or maybe they use the
Earth's magnetic fields to navigate. It's a fascinating mystery for
scientists!
Atlantic salmon leaping over a
waterfall
Salmon migrate to freshwater in late autumn. Make sure you keep
your eye out for them!
For more information on salmon, visit BBC Wildlife Finder and ARKive.