Salmon are thought to use several navigation aids to find their way back to where they were hatched. Scientists believe salmon use a combination of a magnetic orientation, celestial orientation, the memory of their home stream’s unique smell, and a circadian calendar to return to their natal stream to spawn.
Why do salmon return to spawn?
Two factors—water temperature and predation—may drive salmon to return en masse and spawn within a short period of time. Salmon only spawn during open-water seasons and the development rate of eggs and alevins (larval salmon) is directly related to water temperature. Higher water temperatures shorten incubation time.
Salmon can migrate out to sea to feed for several years before returning to spawn in the same stream, sometimes even the same section of stream, in which they were born. Other homing species probably use similar mechanisms, but few can match such precision. How salmon return to the correct shoreline region is not completely understood.
This of course begs the inquiry “Why do salmon change color when they spawn?”
Salmon change color to attract a spawning mate. Pacific salmon use all their energy for returning to their home stream, for making eggs, and digging the nest. Most of them stop eating when they return to freshwater and have no energy left for a return trip to the ocean after spawning.
How do salmon find the right stream to spawn?
Some salmon will try to find the right stream until they use up all their energy and die but most would simply try to find other salmon to spawn with. These fish stray into other streams to spawn if they are lucky.
Why do salmon spawn in streams?
It also allows salmon to spawn somewhere if the stream where they were born no longer exists. Pink salmon and chum salmon both often spawn close to the mouths of small streams. If these streams are diverted by winter storms, as often happens, the returning salmon will stray to a nearby stream.
This begs the query “Why do salmon come back to the stream where they were born?”
Salmon come back to the stream where they were ‘born’ because they ‘know’ it is a good place to spawn ; they won’t waste time looking for a stream with good habitat and other salmon. Scientists believe that salmon navigate by using the earth’s magnetic field like a compass.
What happens to salmon during a salmon run?
Grizzly bear fishes for a salmon during a salmon run. The salmon run is the time when salmon, which have migrated from the ocean, swim to the upper reaches of rivers where they spawn on gravel beds. After spawning, all Pacific salmon and most Atlantic salmon die, and the salmon life cycle starts over again.
Do all Atlantic salmon die after spawning?
Not all Atlantic salmon die after spawning and the ones that do make it can return to the ocean and come back to the river the following year.