海洋表面200至1000公尺的區域，稱為「中水層浮游區」 (mesopelagic zone)，或「__暮光區__ 」(twilight zone)，是介於「光合作用區」(epipelagic zone)以及「半深海區」(bathypelagic zone)的交界區。

接近無光的暮光區裡有很豐富的魚群，當較淺的水域捕獲不到食物時，鯊魚和其他大型魚類便會到這裡攝食。

不同的鯊魚在暮光區待的時間也不同。水鯊最久待一小時。鯨鯊可以待到四小時。象鮫則可以在暮光區待上四個月! 

鯊魚也有可能是因為其他原因進入暮光區。以鯨鯊為例，他們到暮光區不僅是餵食，也是為了降低體溫，擺脫寄生蟲，保存體力，甚至重新校正體內導航系統。

__出處:__
https://www.whoi.edu/press-room/news-release/shark-week-2021-sharks-and-the-oceans-twilight-zone/


The __twilight zone__, also called the Mesopelagic zone, begins at the depth where only 1% of incident light reaches (200 m/ 645 feet) and ends where there is no light (1000m/3280 feet). It is home to some of the largest fish biomass on Earth, making it a unique feeding ground for the ocean’s largest predators.  Many shark species venture from surface waters to the deep ocean between 200 and 1000 meters (656 to 3280 feet) and experts believe the main purpose is to hunt for prey when food is scarce in surface waters.

Different shark species spend varying lengths of time in the twilight zone. Blue sharks spend up to an hour hunting for a meal; whale sharks can spend a few hours; and basking sharks take it to the extreme, spending up to four months feasting on twilight zone creatures before reemerging to the sunlit surface waters.

There could be other reasons for sharks to visit the twilight zone.  For example,  besides feeding,  whale sharks visit the twilight zone to cool down, remove parasites, save energy, or even to calibrate their internal navigation.

__Source:__
https://www.whoi.edu/press-room/news-release/shark-week-2021-sharks-and-the-oceans-twilight-zone/


暮光區的鯊魚

Twilight zone sharks

鯊魚為什麼去幾乎無光的暮光區?牠們去那裏做甚麼?

Why do sharks go to the almost lightless twilight zone and how long do they stay there for?

鯊魚在暮光區待多久呢?

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