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Once everything is set up, he turns on the power.
一切就绪后，他会打开电源。
Now a small electric field is emanating from the experiment.
现在，实验产生了一个小电场。
Think of it like an invisible campfire on the sandy bottom.
把它想象成沙子底部看不见的篝火。
It's only warm if you are close.
只有靠得近才会感到暖和。
The sharks swim by, but they don't detect it any more than we do.
鲨鱼游过，但它们和我们一样没有察觉到。
They are way too high above it in the water column to realize that anything is happening.
它们在水柱中的位置过高，意识不到正在发生的事情。
After lunch, Connor, our shark handler, shows up with some bait.
午饭后，我们的鲨鱼管理员康纳带着鱼饵出现了。
He will use the bait to get the sharks closer to our electrical campfire.
他会用诱饵让鲨鱼靠近我们的电子篝火。
The sharks are hungry, so they will focus their attention on Connor, close to the sandy bottom.
鲨鱼很饿，所以它们会把注意力集中在靠近沙质海底的康纳身上。
The Lemon sharks are swimming close to the bottom now, looking for food.
柠檬鲨正贴近海底游泳，寻找食物。
Dr. Kajiura turns on the power and we watch.
卡久拉博士打开电源，我们看着。
The very first Lemon shark to pass over immediately takes an interest in the plexiglass.
第一条游过的柠檬鲨立刻对有机玻璃产生了兴趣。
It can clearly feel the tiny electrical field.
它能清楚地感受到微小的电场。
A Tiger shark passes half a meter above the experiment and doesn't react.
虎鲨在实验场上方半米处通过，没有反应。
But another Lemon shark cruising just above the sand homes right in on it.
但另一条柠檬鲨就在沙底上方游弋。
The apparatus is designed to produce an extremely small electrical field, similar to the one generated by a living thing.
设计这个装置是用来产生一个非常小的电场，类似于生物产生的电场。
We are talking about a super tiny current.
我们说的是一个超微小的电流。
Shark after shark stops to check it out--even while Connor is feeding the sharks only a few meters away--but only the sharks that are swimming close enough to the sand to feel it.
鲨鱼一条接一条地停下来查看，康纳就在几米外喂鲨鱼，但只有那些游得足够近的鲨鱼能感觉到它。
This demonstrates how the electrosensory system of sharks is only good for close range because the electrical field doesn't carry far in the water.
这说明鲨鱼的电感应系统只适合近距离使用，因为电场不会在水中传播太远。
They need to use their other senses like hearing, eyesight, and scent to get close enough to prey for the electrosensory system to work.
它们需要利用听觉、视觉和嗅觉等其他感官，以足够接近猎物，使电感应系统工作。
Sharks are amazing animals.
鲨鱼是神奇的动物。
They have highly-evolved senses to find prey.
它们拥有高度进化的感官来寻找猎物。
Ultra-sensitive eyes that can see in low light.
超敏感的眼睛，可以在微光下看到物体。
A powerful sense of smell.
效力强大的嗅觉。
They can detect the slightest vibrations in the water that might be quarry.
它们能探测到水里潜在猎物最轻微的振动。
And when they get close to the prey--even in pitch darkness--they have the ability to detect electrical fields.
当它们接近猎物时，即使在漆黑的环境中，它们也能探测到电场。
Some people think that because sharks have been around for hundreds of millions of years that they are in some way primitive.
有些人认为，因为鲨鱼已经存在数亿年，所以它们在某种程度上是原始生物。
But that's completely wrong.
但这完全错误的。
Because they have been around for so long, they have developed these incredible senses to give them the upper hand in the struggle for life in the Blue World.
因为它们存在了这么久，已经发展出这些不可思议的感觉，让它们为在蓝色世界的生活中奋斗占据上风。
