The world's biggest living fish is a shark.

世上最大的魚，是鯊魚。

Of the estimated 34,000 species of fish, the largest are whale sharks.

就估計，鯊魚約有三萬四千個品種，其中最大的是鯨鯊。

These gentle giants usually grow to about 40 feet long and weigh an estimated 15 tons.

這些溫柔的巨魚，通常可以長至四十英尺 (約一千兩百公分)，且重達十五噸。

Their mouths alone can span four feet wide.

光是他們的嘴巴，就可以張開到四英呎 (約一百二十公分)。

The gigantic whale shark, however, pales in comparison to the largest fish that ever existed, the megalodon.

然而相較於史上存在過最大的魚——巨牙鯊，巨大的鯨鯊不算什麼。

Dating to over 20 million years ago, it's thought that the prehistoric shark could've reached 80 feet long, weighing up to around 70 tons.

回溯到兩千萬年前，史前的鯊魚可以長至八十英呎長 (兩千四百公分)，且重達七十噸。

Unlike whale sharks, the megalodon was carnivorous, and consumed any creature that fit into it's nearly 10 foot-wide mouth.

與鯨鯊不同的是，巨牙鯊是食肉動物，任何能進入他十英呎寬 (三百公分) 嘴巴裡的生物，他都吃。

Throughout their lives some species of shark can shed over 30,000 teeth.

在鯊魚的一生中，有些品種的鯊魚可以換超過三萬顆牙齒。

Unlike humans who are born with a set number of teeth in their jaws, sharks have a seemingly limitless supply.

不像人類在下顎上有固定的一組牙齒，鯊魚似乎有無盡的替換牙齒。

They can grow, lose, and replace their teeth as needed.

如果需要的話，他們可以生長、失去、替換牙齒。

Furthermore, most sharks have multiple rows of teeth in their jaws.

而且，大部份的鯊魚在下顎都有好幾排牙齒。

The jaws of a great white shark, the largest predatory fish in the sea, can contain up to seven rows that hold up to 300 teeth at any one point.

海洋中最大的捕食性魚類——大白鯊，有七排牙齒，一次擁有高達三百顆牙。

Most sharks, as they hunt their prey, end up losing their teeth individually.

大部份的鯊魚在獵食時，最後都會一顆一顆失去牙齒。

However, the cookiecutter shark loses and replaces the teeth in it's lower jaw all at once.

不過，巴西達摩鯊一次會補進整排下顎的牙齒。

Sharks are built for speed.

鯊魚的強項是速度。

The fastest known shark, the mako shark, can reach speeds of up to 46 miles per hour.

最快的鯊魚——尖吻鲭鲨，有高達四十六哩 (約七十四公里) 的時速。

This speed is largely due to their body's hydrodynamic design.

他們的速度快的原因，大多是由於身體的流體構造。

Many sharks have torpedo shaped heads that allow them to cut through the water with little resistance.

許多鯊魚都有魚雷般的頭部，可以讓他們不受太多阻力地游泳。

Plus, shark skin is covered with flat, v-shaped scales, called dermal denticles.

再加上鯊魚皮被平坦的、Ｖ 字型的魚鱗包覆。這種魚鱗叫做盾鱗。

The denticles help water flow smoothly over the skin, which reduces friction and helps sharks swim quickly and quietly.

盾鱗幫助水滑順的流過皮膚，可以減少摩擦，幫助鯊魚游得快且安靜。

Sharks also have skeletons made of cartilage instead of bone.

鯊魚的骨骼是軟骨做的，並非一般骨頭。

Cartilage is a much lighter material than bone so sharks have less weight to carry.

軟骨的材質比骨頭輕多了，所以鯊魚不需要太負重。

Sharks may lay eggs, or bear live young.

有些鯊魚是卵生，有些是卵胎生。

Egg laying sharks only lay a few large eggs.

會產卵的鯊魚只會產下一些大型的卵。

They may come in various forms, such as sacks called mermaid purses, or corkscrews.

他們有許多樣子，像是被稱為美人魚皮包、螺絲起子的布袋狀的卵。

These eggs act as external wombs in which shark embryos complete their development.

這些卵就是外部的子宮，鯊魚的受精卵會在裡頭完成發育。

However, most sharks give birth to live young.

不過，大部份的鯊魚屬於卵胎生。

Called pups, the young of most live-bearing species gestate for around one year.

大部份的卵胎生都會在媽媽體內孵育大約一年，他們叫做幼仔。

Some even begin practicing their predation skills while in the womb.

有些甚至在子宮裡時，就在練習獵食技巧了。

Before they are born, the sand tiger shark pups compete with their siblings.

在沙虎鯊出生之前，他們的幼仔就會與兄弟姊妹競爭了。

In fact, the strongest pup in each of the two wombs devours its weaker brothers and sister.

事實上，在兩個子宮內的最強幼仔，會把更弱的弟弟或妹妹吃掉。

Some sharks are at risk of extinction.

有些鯊魚面臨絕種的危機。

Every year an estimated 100 million sharks are killed worldwide, in large part for the shark fin trade.

每年全球大約有一億隻鯊魚被殺，大多是為了魚翅交易。

The sharks are caught and their dorsal fins are removed and sold at a hefty price, primarily in Asia.

主要發生在亞洲，有些鯊魚被抓住後，背鰭被割下、以高價售出。

In traditional Chinese culture, serving and eating shark fin is a sign of status and wealth.

在傳統中國文化裡，吃得起魚翅是社會地位與財富的象徵。

Because of the high demand and value of shark fins, some shark populations have plummeted by up to 70 percent, causing a ripple effect in ecosystems and endangering at least 74 shark species.

由於魚翅的高需求與高價，在生物系統裡，有些鯊魚的數量已經落到只剩百分之三十，至少有七十四個鯊魚品種備受危害。

However, measures are being taken to protect sharks, with a number of countries and jurisdictions cracking down on unsustainable shark fishing.

然而，一些國家和轄區有採取保護鯊魚的措施，對抗不能永續的鯊魚獵捕行為。

In China, shark fin soup is no longer allowed to be served at government banquets.

在中國，魚翅湯被禁止在政府宴會上出現。

A move hailed by shark conservationists.

一個被鯊魚保育者喝采的行為。

Through continued international conservation efforts, the loss of sharks may be curbed, allowing the creatures in all their power and grace to survive for many generations to come.

透過持續的國際保育努力，鯊魚的死亡也許能被遏止，讓這些有力又優雅的生物得以生生不息。