Meet the bluefin tuna, the toughest fish in the sea - Grantly Galland and Raiana McKinney

翻译人员: Lingyan Ning 校对人员: Helen Chang

What’s as big as a polar bear, swallows its prey whole,

什么的体型和北极熊一样大

能一口吞下它的猎物

and swims at 40 miles an hour?

游泳时速可达40英里？

It’s not a shark or a killer whale.

它不是鲨鱼或杀人鲸

It’s the Atlantic bluefin tuna.

它是大西洋蓝鳍金枪鱼

The largest and longest-lived of the 15 tuna species,

是现存的15种金枪鱼中 体型最大、身长最长的

the Atlantic bluefin has a unique set of adaptations

大西洋蓝鳍金枪鱼 有它自己独特的适应机制

that make it one of the most dominant predators in the ocean.

使它成为了海中主要的捕食者之一

It starts as a tiny hatchling in the Gulf of Mexico or the Mediterranean Sea,

它在地中海或是墨西哥湾中孵化

no bigger than a human eyelash.

幼年形态极小 与人类的眼睫毛一般大小

Within its first year of life,

在它的第一年里

It develops something known as regional endothermy—

它学会了一项本领——局部体温调节

the ability to regulate its body temperature.

它可以调节自身体温

An Atlantic bluefin gets oxygen from cold ocean water using its gills.

蓝鳍金枪鱼通过鳃 从冰冷的海水中滤出氧气

This process cools its blood.

这一过程会使它的血液冷却

Then, heat the tuna generates swimming and hunting warms the blood.

同时，金枪鱼通过游泳和捕猎 使自身血液升温

In most fishes, this heat would be lost back out into the ocean through the gills.

大多数鱼类的热量通过鳃 散失到海洋里了

But in the Atlantic bluefin,

但在蓝鳍金枪鱼身上

a mechanism called countercurrent exchange traps the heat.

有一种名为逆流交换的机制 可以捕获这些热量

Cold blood on its way to the large swimming muscles

流向大块游泳肌肉的冷血

passes close to warm blood leaving those muscles

与离开这些肌肉的温血很靠近

in a specialized network of blood vessels known as a rete mirabile.

那高度特化的血管网称为细脉网

Here the heat “jumps” to the cold blood and stays in the body.

在这里，热量由温血“跃”至冷血 继续保留在身体中

This makes bluefin one of the few warm-blooded fishes,

这使得蓝鳍鱼成为了 为数不多的的温血鱼类

a huge advantage in the marine environment.

正是它在海洋生存的一大优势

Cold-blooded animals whose body temperature

冷血鱼类的体温

depends entirely on the environment become sluggish in colder waters.

完全取决于环境温度

在低温海水中，它们会变得活动迟缓

But a bluefin’s ability to keep warm means it has sharper vision,

但蓝鳍鱼有维持体温的本领 意味着它们视力更敏锐

can better process information, and can swim faster than its prey.

处理信息更快 游得比猎物更快

It thrives in cold, deep, subarctic water.

得以在冰冷的亚北极地区的深海 生长壮大

Thanks to their warm bloodedness, their powerful muscles,

得益于它们的温血系统 它们拥有了发达的肌肉

and their streamlined torpedo shape

拥有了如鱼雷般流线型的身形

with fins that fold into grooves to reduce drag,

以及可以折叠进凹槽的鱼鳍来减小阻力

bluefin tuna can reach speeds few other animals can match.

蓝鳍金枪鱼的速度少有动物能及

Their maximum speed of 40 miles per hour

它们最高时速可达40英里

is faster than that of a great white shark or orca whale,

比大白鲨或是杀人鲸还要快

and even at their comfortable cruising speed,

即使是以它们日常的巡航速度

they can cross the Atlantic in a couple months.

也可以在两个月内横跨大西洋

All this swimming requires a great deal of oxygen,

所有游泳都需要耗费大量氧气

but the bluefin is adapted for this as well.

但蓝鳍鱼对此也适应得很好

The faster it swims, the more water passes over its gills,

它游得越快，流经鳃的水就越多

and the more oxygen it can absorb from that water.

它可以从海水中获取的氧气就越多

This need for a constant flow of water

这要求它要始终处于流水中

means the tuna must always remain on the move.

意味着蓝鳍金枪鱼 必须时刻保持运动状态

It also means bluefin cannot suck prey into their mouths

同时这也意味着蓝鳍金枪鱼 不能像其他大多数鱼类一样

the way most other fishes do.

用口吸入猎物

Instead, they must chase down their prey with their mouths open.

恰恰相反，它们在追逐猎物的过程中 始终大张着嘴巴

They eat smaller prey than most predators their size,

相比起与它们同等大小的捕食者 它们吃的的猎物体型更小

including squid, crustaceans, and smaller fish species like mackerel.

包括乌贼、甲壳动物 以及如鲭等小型鱼类

The bluefin’s temperature-regulating ability

蓝鳍金枪鱼的体温调节能力

doesn’t just make it a superior hunter— it gives it nearly unlimited range.

并不仅仅是助其成为出色的捕猎者 这一本领给它的远不止这些

As soon as they’re strong enough to swim against the current,

当蓝鳍金枪鱼强壮到足以逆洋流而行时

Atlantic bluefin leave the warm waters of their spawning grounds

它们会离开适宜产卵的温暖流域

and spend their lives hunting all over the Atlantic Ocean.

将捕猎范围扩大到整个大西洋

Tunas from both the Gulf of Mexico and the Mediterranean Sea

孵化自墨西哥湾和地中海的金枪鱼

frequent the same feeding grounds

经常出没于同样的觅食区域

and range from Brazil and Texas to Iceland and Senegal and beyond.

下至巴西、德克萨斯州， 上至冰岛、塞内加尔或是更北的地区

But when the time comes to reproduce around age 10,

但当它们到了大约10岁—— 产卵繁殖的年纪

they always return to their sea of origin.

它们总是会回到出生的海域

Here, groups of males and females release millions of eggs and sperm

在这里，成群结队的雌鱼和雄鱼 在水中产下它们的卵子和精子

into the water.

They’ll migrate back and forth between feeding and spawning grounds

在余下的年岁中

它们会来回往返于觅食区域和产卵地

annually for the rest of their lives.

Atlantic bluefin can live for over 40 years, growing all the while.

大西洋蓝鳍金枪鱼寿命可达40余年 终身都在生长

The largest specimens are tens of millions of times heavier than when they hatched.

最大的蓝鳍鱼标本的体重 是它们刚孵化时的千万倍

The same huge size that makes bluefin tuna indomitable in the ocean

其巨型身形使其海中霸主的地位 不可动摇

has made them vulnerable to one predator in particular: us.

但也令其在面对唯一的捕食者 我们人类时非常脆弱

Humans have a long history of fishing Atlantic bluefin—

人类捕杀大西洋蓝鳍金枪鱼的历史 由来已久——

it’s even stamped on ancient Greek coins.

古希腊的钱币上就印有蓝鳍金枪鱼

But in recent decades, demand has skyrocketed

但在近几十年间，需求量猛然上涨

as bluefin are hunted for sashimi, sushi, and tuna steaks.

是因为蓝鳍鱼可做成刺身、 寿司、金枪鱼排

An individual fish can sell for $10,000 or more,

单单一条金枪鱼的售价 可高达10000美元甚至更高

promoting overfishing and illegal fishing.

过高的售价进一步加剧了 过度捕捞和违法捕捞

But if recent conservation efforts are redoubled and quotas are better enforced,

不过，如果近年来的保护力度加倍 并更好地执行配额捕捞

bluefin populations can begin to recover.

蓝鳍金枪鱼的种群还是可以逐渐恢复