VOA慢速英语2020 科学家计算世界上最大的鱼的年龄（在线收听）

Scientists Estimate Age of World’s Largest Fish

Scientists have recently discovered how to compute the age of whale sharks, Earths largest fish.

科学家们最近发现了如何计算地球上最大的鱼类——鲸鲨的年龄。 

Researchers used information about radioactivity levels from Cold War-era atomic bomb testing.

研究人员利用了冷战时期原子弹试验的放射性水平信息。 

They determined that bands form in the shark vertebrae every year, like a trees growth rings.

他们确定，每年鲨鱼的椎骨都会形成条纹，就像树木的年轮一样。 

They reached their conclusion by measuring levels of carbon-14.

他们通过测量碳14水平得出了结论。 

The naturally occurring radioactive element is also a product of nuclear explosions.

天然存在的放射性元素也是核爆炸的产物。 

It was already known that these bands existed and increased in number as sharks aged.

人们已经知道，鲨鱼条纹的存在，并且随着年龄的增长，条纹的数量也在增加。 

But it was unclear whether new rings appeared yearly or every six months.

但尚不清楚新年轮是每年出现一圈，还是每六个月出现一圈。 

The researchers compared carbon-14 levels in the rings to data on changes in carbon-14 levels over time.

研究人员将年轮中的碳14水平与碳14水平随时间变化的数据进行了比较。 

They compared them, especially, to the years of atmospheric nuclear tests in the 1950s and 1960s.

他们特别将其与20世纪50年代和60年代的大气核试验进行了比较。 

Joyce Ong is a marine scientist at Rutgers University in New Jersey.

乔伊斯·昂是新泽西州罗格斯大学的海洋科学家。 

She was the lead author of the study that was published recently in the journal Frontiers in Marine Science.

她是最近发表在《海洋科学前沿》杂志上的一项研究的主要作者。 

"These elevated levels of carbon-14 first saturated the atmosphere,then oceans and moved through food webs into animals,

昂说：“这些升高水平的碳14首先渗透到大气中，然后进入海洋，通过食物网进入动物体内， 

producing elevated levels in structures such as the vertebrae of whale sharks," Ong said.

在鲸鲨的脊椎等结构中产生了升高水平的碳14。” 

Whale sharks have a brownish-grayish color on the back and sides with white spots.

鲸鲨的背部和侧面呈灰褐色，有白色斑点。 

The largest ones measure some 18 meters in length.

最大的有18米长。 

They swim great distances through the worlds tropical oceans to find food and feed on small organisms taken out of the water.

它们在全球热带海洋中游了很长的距离来寻找食物，并以从水里捞出来的小生物为食。 

The discovery enables scientists to measure a whale sharks age after its death.

这一发现使科学家能够测量鲸鲨死后的年龄。 

But just as importantly, it shows that these endangered marine giants grow slowly.

但同样重要的是，它表明这些濒临灭绝的海洋巨物生长缓慢。 

Mark Meekan, a co-author, is with the Australian Institute of Marine Science in Perth.

合著者马克·米坎就职于珀斯的澳大利亚海洋科学研究所。 

He said, "For the management of any marine species,

他说：“对任何海洋物种的管理来说， 

knowledge of growth rate is critical as it determines the resilience of populations to threats such as fishing."

了解增长率至关重要，因为它决定了种群对诸如捕鱼等威胁的恢复能力。” 

Meekan said, "We thought that it was possible that they could reach ages of as much as 100 years, but we werent really sure..."

米坎说：“我们认为它们有可能活到100岁，但我们并不确定……” 

The researchers tested carbon-14 levels in long-dead whale sharks whose remains were stored in laboratories.

研究人员测试了死亡已久的鲸鲨体内的碳14含量。这些鲸鲨的尸体被储存在实验室里。 

The oldest one tested, stored in Pakistan, had lived 50 years.

被检测的最年老的鲸鲨储存在巴基斯坦的实验室里，它活了50年。 

Im John Russell.

约翰·拉塞尔为您播报。