No one has ever been able to witness freshwater eels spawning, and for eel biologists, solving this eel-reproduction mystery remains a kind of holy grail.

从来没有人亲眼见到淡水鳗鱼产卵。对鳗鱼学家来说，鳗鱼神秘的繁殖习惯依然是个难解之谜。

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There are hundreds of different species of eel, all of which can be roughly divided into two groups according to their habitat: saltwater and freshwater.

鳗鱼的种类有数百种，根据其栖息地大致可以分为两类：咸水鳗鱼和淡水鳗鱼。

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Some exceptional species are sensitive to ultrasound, while others such as the European eel, a freshwater species that spawns at sea, are sensitive to infrasound.

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