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WonderAnimal migration fact

European eels live in the rivers of Europe and North Africa but begin life some 5,000 kilometres away in the Sargasso Sea, in the western Atlantic. Adults swim back there to breed, yet no one has ever seen them spawn.

European eel migration

MigrationOceanBiologyEvolutionScience

The story behind the card

How eels breed puzzled people for more than 2,000 years; Aristotle thought they arose from mud. In the early 1900s the Danish biologist Johannes Schmidt spent almost two decades netting eel larvae across the Atlantic and found that they grew smaller the further west he went, until the tiniest turned up only in the Sargasso Sea. The larvae drift to Europe with the Gulf Stream and turn into transparent 'glass eels' as they near the coast. In 2022 researchers reported the first direct evidence of adults reaching the Sargasso Sea, after tracking satellite-tagged eels released in the Azores. No eggs or spawning adults have yet been found. The species is now critically endangered.

Türkçe oku
Avrupa yılan balıkları Avrupa ve Kuzey Afrika'nın nehirlerinde yaşar, ama hayata yaklaşık 5.000 kilometre ötede, Atlas Okyanusu'nun batısındaki Sargasso Denizi'nde başlar. Yetişkinler üremek için oraya geri yüzer; yine de onları yumurtlarken gören olmamıştır.

Yılan balıklarının nasıl ürediği 2.000 yılı aşkın bir süre çözülemedi; Aristoteles onların çamurdan doğduğunu düşünüyordu. 1900'lerin başında Danimarkalı biyolog Johannes Schmidt yaklaşık yirmi yıl boyunca Atlas Okyanusu'nda yılan balığı larvası topladı. Batıya gittikçe larvalar küçülüyordu; en küçükleri yalnızca Sargasso Denizi'nde çıktı. Larvalar Golf Akıntısı'yla Avrupa'ya sürüklenir ve kıyıya yaklaşınca “cam yılan balığı” denen saydam yavrulara dönüşür. 2022'de araştırmacılar, Azor Adaları'nda uydu vericisi takılıp salınan yılan balıklarını izleyerek yetişkinlerin Sargasso Denizi'ne ulaştığını ilk kez doğrudan gösterdi. Ama henüz ne yumurta ne de yumurtlayan bir yetişkin bulundu. Tür bugün kritik tehlike altındadır.

Sources and further reading

Background reading: European eel
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