Salmon - an epic journey

Salmon - an epic journey

A strange and amazing tale of fishy survival.

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 Atlantic salmon emerging from stream bed. Photo by US FWS - northeast region

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

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!

Salmon leaping up waterfall_dv416005

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.