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Salmon that spend only one year before returning
to spawn do not move very far from their home rivers. They remain in
coastal areas, or off the coast along the continental shelf. However,
the salmon that spend two years at sea, from both the European and North
American side of the Atlantic Ocean, move to feeding pastures either
off the coast of Greenland, or off the Faeroe Islands. Tagging studies
showed that fish from North America are most numerous at Greenland,
but European fish are also present. Off the Faeroe Islands, fish from
the European side of the Atlantic are most common, but a few North American
fish are also present.
Salmon home back to the river, or even to the specific
tributaries, in which they were born to spawn. Because of this they
become genetically unique. Scientists have proven this by examining
the salmon DNA. (You can get DNA without hurting the fish by taking
a little clip with scissors from one of the fins.) The salmon are believed
to home back to their rivers using a variety of cues to do this. Studies
of tagged salmon show there is very little straying, even to neighboring
rivers.
The salmon’s sense of smell is strong, and
they may be able to smell their home rivers. As well, they can detect
magnetic fields and may use this as some sort of a compass. They can
also see polarized light, and this can be used in some instances to
orient oneself. Finally, where landmarks are present, the salmon may
remember the way they went to go to the feeding grounds, and follow
the same path back.
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