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Salmon may cross the ocean with a magnetic compass, then use smell to find the stream where their life began.

U.S. Geological Survey / NOAA

ScienceNature

The story behind the card

Pacific salmon hatch in rivers, spend several years at sea, then return to spawn, often in the very stream where they were born. Scientists think they use at least two senses. At sea, the Earth's magnetic field seems to guide them: a 2013 study of sockeye salmon returning to Canada's Fraser River found that the route they took around Vancouver Island shifted with slow changes in the magnetic field, as if they had memorised the field at their river mouth. Near the coast, smell takes over. In the 1950s the American biologist Arthur Hasler found evidence that young salmon learn the particular scent of their home stream and follow it back as adults.

Türkçe oku
Somon balıkları okyanusta Dünya'nın manyetik alanını bir pusula gibi kullanabilir; eve yaklaşınca da doğdukları derenin kokusunu izler.

Pasifik somonları nehirlerde yumurtadan çıkar, birkaç yılı denizde geçirir, sonra yumurtlamak için çoğu zaman tam da doğdukları dereye döner. Bilim insanlarına göre yollarını en az iki duyuyla bulurlar. Açık denizde Dünya'nın manyetik alanı onlara yol gösteriyor gibidir: Kanada'daki Fraser Nehri'ne dönen kırmızı somonlar (sockeye) üzerine 2013'te yapılan bir araştırma, balıkların Vancouver Adası'nın hangi yanından geçeceğinin manyetik alandaki yavaş değişimlere göre kaydığını gösterdi; sanki nehir ağzındaki manyetik alanı ezberlemişlerdi. Kıyıya yaklaşınca koku devreye girer. Amerikalı biyolog Arthur Hasler 1950'lerde, yavru somonların doğdukları derenin kendine özgü kokusunu öğrendiğine ve erişkin olunca bu kokuyu izleyerek geri döndüğüne dair kanıtlar buldu.

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Background reading: Salmon run
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