Name: TED-Ed】鰻魚的埃利。一個神祕的遷徙--詹姆斯-普羅塞克 (【TED-Ed】Eli the eel: A mysterious migration - James Prosek)
Uploaded: 2021-01-14T05:19:40.000Z
Duration: 4 min 39 s

They're long and slithery, and they're not very colorful.

牠們很修長，全身滑溜溜，而且沒有鮮艷的色彩。 

But they do have a strange beauty of their own.

但是牠們俱有一種獨特的美感。

Their sinuous, nocturnal movements through the water are mesmerizing to watch.

夜裡，牠們在水中彎曲地移動， 令人歎為觀止。 

And though they may resemble underwater snakes, eels are, in fact, a very interesting type of fish.

雖然牠們很像水蛇，實際上，牠們是鰻魚，一種很特別的魚類。 

There are several things about eels that make them unique besides their elongated shape and limbless bodies.

除了修長的身形，沒有四肢外，鰻魚有許多特徵 讓牠們看起來獨一無二。 

For one thing, eels have the ability to breathe through their skin.

首先，鰻魚可以透過皮膚呼吸。 

Some can even leave the water and move over land for short periods.

有的甚至可以離開水面在陸地上存活一小段時間。 

And, unlike most migratory fish, such as salmon, which spawn in fresh water.

不像大部分有遷移習性的魚類，如鮭魚， 在淡水中產卵 

but live their adult lives in salt water,

eels of the genus Anguilla migrate in the opposite direction, spawning and breeding in oceans and seas, while spending most of their intervening time in fresh water.

安圭拉島的鰻魚以相反的方向遷移， 牠們在海洋中產卵和繁殖， 大部分的時間 在淡水中成長。 

If we were to take one such fresh water eel and follow its life story, it would be born in the middle of the North Atlantic Ocean, about a thousand miles east of Bermuda.

如果我們跟隨一條淡水鰻魚來了解牠的生活故事， 那就是牠出生於北太西洋中，游到百慕達的東部約 1000 英哩的地方，  

This area, called the Sargasso Sea, forms the western part of a subtropical gyre, a giant whirlpool in the middle of the ocean.

這個區域，稱為馬尾藻海，也就是亞熱帶環流 的西半部， 在海洋中有一個巨大的漩渦。 

Our eel, let's call it Eli, would begin as one of ten to twenty million tiny eggs, carried by a female eel, hatching into a transparent leaf-shaped thing that looks nothing like an adult eel.

讓我們稱這條鰻魚為伊萊，當雌鰻魚帶著這個千萬分之一的小卵時， 牠的生命由此開始， 然後孵化成透明且葉子形狀的東西 這看起來一點也不像鰻魚。 

Eli starts to drift in ocean currents, predominantly the Gulf Stream towards either Europe or North America, depending on its particular species.

伊萊隨著海潮漂流，順著墨西哥灣流的方向 依種類的不同 游向歐洲或北美洲。 

Upon reaching the coast, Eli is about two inches long, looking more eely but still transparent, known at this stage as a glass eel.

當到達岸邊時，伊萊大約有兩英吋長了， 這時形狀看起來比較像鰻魚， 但仍然是透明的身體， 這個時期，大家稱牠為玻璃鰻。 

But within a couple of days in fresh water, Eli's skin becomes pigmented a brownish-black, now looking more like that of an adult eel.

但生活在淡水的幾天後，伊萊的皮膚變成無光澤的黑褐色， 這時看起來比較像鰻魚。 

You might notice that we haven't mentioned anything about Eli's gender yet.

你也許注意到一件事我們還沒提到 伊萊的性別。 

That's because this is only determined once an eel enters fresh water, though nobody is sure exactly how that happens.

這是因為性別是在鰻魚進入淡水時的情況而定， 沒有人能確切知道真實的狀況。 

Most of the eels that stay in the estuaries and brackish water become males, while those that go upstream become females, growing up to two to three times bigger than their future mates.

大部分的鰻魚會停留在出海口，帶有微鹹的水域讓鰻魚變成雄性， 那些往河流上游游去的鰻魚變成雌性， 雌鰻魚會長到比未來的配偶 還要大上兩至三倍。 

In this case, it turns out that Eli was actually short for Elaine.

在這個情況下，伊萊變成是‎伊萊恩。 

As a female eel, Elaine will be quite solitary for most of her life in the stream,

一條雌鰻魚，‎伊萊恩在大部分時間 獨來獨往地生活於淡水河中， 

eating whatever falls in the water: grasshoppers, crickets, small fish, insect larvae, frogs, baby birds, almost anything she can get her mouth around.

牠吃任何掉入水中的東西：蚱蜢，蟋蟀，小魚， 幼蟲，青蛙，雛鳥， 任何她嘴巴能輕易取得的東西。 

And she will grow quite big, up to four feet long and weighing as much as thirteen pounds.

她可以長得相當大，直到四呎長 重量達十三磅。 

We don't know exactly how fresh water eels know when it's time to return to the ocean, but something calls to them.

我們無法確切得知在淡水中生活的鰻魚， 怎會知道何時要回到海洋， 一定有某種力量在召喚牠們。 

And their fall migration is one of the largest unseen migrations on the planet.

牠們的秋季遷移是地球上 前所未見的大遷移之一。 

As Elaine leaves fresh water for the ocean, she undergoes a shocking metamorphosis.

當‎伊萊恩離開淡水游往海洋，她經歷一個令人驚訝的蛻變。 

Her eyes enlarge by about ten times, her skin gets thicker, and her fins get larger.

她的眼睛變大十倍，皮膚變得比較厚， 鰭也變得更大。 

These are most likely adaptations for their upcoming ocean travel, and Elaine seamlessly makes the transition from fresh to salt water, which would be toxic for most other fish.

這是為了適應牠將在海洋中的旅程所做的變化， 從淡水到鹹水的過程中 ‎伊萊恩悄悄地做了轉變， 但鹹水對大部分的魚類來說是有害的。 

Once Elaine leaves the mouth of the fresh water streams, she will disappear completely from human view.

‎一旦伊萊恩離開淡水河口，她就完全消失在人類的視線中。 

No one has witnessed, or been able to follow, an adult eel on their migration, nor do we know how deep they spawn.

沒有人目睹，或跟蹤 一條成人鰻魚的遷移， 我們不知牠們在多深的海域產卵。 

But it's assumed that they can follow some signs that they can detect, such as a thermal barrier between ocean currents or a salinity front, in order to return to the same area of the ocean where they were born.

假設牠們能夠偵測訊號，然後隨著這些訊號游回海洋， 如：洋流之間的熱障 或是鹽度， 這是為了回到 牠們出生的海洋。 

Because we don't even know exactly what happens during an eel's migration, we can only imagine what the actual breeding looks like.

我們不是很了解在鰻魚遷移當中，發生了什麼事， 我們只能想像牠繁殖的情況。 

But the common hypothesis is that Elaine and thousands, or hundreds of thousands, of other eels gather in large, intertwined masses and release their eggs and sperm in a giant orgy known as panmixia.

一般的假設是：‎伊萊恩和數千個的， 或成千上萬的 其他鰻魚 聚集成一大群，互相糾纏在一起 儘情地進行隨機交配， 然後產出卵子和精子。 

A couple of days after the eggs are laid, they hatch, and the cycle begins again.

卵被生下的幾天後，牠們孵化了， 然後又再次循環這個過程。 

And because we've never seen the adult eels returning up the fresh water rivers,

因為我們從沒目睹過成年鰻魚游回淡水河的情形， 

we must assume that, having completed their long and roundabout journey, these amazing and mysterious creatures finally die there, in the same place where they were born.

我們必需如此假設：這些神奇且神秘的生物， 在完成長途且曲折的旅程後， 最後消逝 在牠們出生的海洋中。 

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TED-Ed】鰻魚的埃利。一個神祕的遷徙--詹姆斯-普羅塞克 (【TED-Ed】Eli the eel: A mysterious migration - James Prosek)

giant

long

adult

bear