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VOA标准英语2010年-Invasive Asian Carp Threaten Ecosystem

时间:2010-08-09 07:10来源:互联网 提供网友:dy7653   字体: [ ]
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Asian Carp now outnumber native fish in many areas of the United States and their expansion particularly threatens the fragile ecosystems2 of the Great Lakes.

In an effort to control algae3 growth, catfish4 farmers in the southern United States introduced Asian Carp - a species of fish found in China - into their ponds in the 1970s.  Flooding throughout the last several decades washed the fish out of those ponds into other waterways.  Gradually, the species multiplied and spread north along major rivers such as the Mississippi and the Illinois. 

Anywhere else in the world, this would be a fisherman's dream, rivers so abundant with fish they jump out of the water, and often right into the boat.  But these are not the kind of fish that get anglers in the United States excited.  They are known as Asian Carp and the explosion of their population in the Illinois River is a concern to large-river ecologist Kevin Irons.

"They compete with every other fish that's in our water," said Irons.  Irons is part of a team with the Illinois Natural History Survey, which is spearheading an effort to kill or contain Asian Carp before they reach Lake Michigan.  The group routinely patrols the Illinois River near Havana - searching for Asian Carp, which are not hard to find.  To understand where and how much the invasive species is spreading, Irons and his crew use a method known as electro fishing to stun5 the Asian Carp so they can be captured and counted.

 

"There's as many as 4,100 adult silver carp per mile here on the middle Illinois River," said Irons.  "So they very quickly turn into about 13 tons per mile, and when you look at an eighty mile [129 kilometer] reach, it's phenomenal how much bio mass is taken up by these Asian Carp."

There are two types of Asian Carp in the Illinois River - bighead and silver.  Both eat the same food as other - native - fish, such as catfish and buffalo6.  Asian Carp can weigh up to 45 kilograms each, and eat up to half their body weight in food per day.

Gradually, Asian Carp edge out the other native species in the river until they are one of the only kinds of fish left.  It is catastrophic to the natural ecosystem1, and a problem for the fishing industry in the U.S., which looks at Asian Carp as an undesirable7 fish to eat.

"Americans in general don't like a bony fish," said Irons.  "The rest of the world eats silver carp, they're actually the most cultured fish in the world.  And they're overfished almost everywhere because they are so desired for human consumption."

With no natural predator8 in the water, and almost no domestic market to sell them as food, Asian Carp threaten to expand into waterways through the city of Chicago, and into Lake Michigan, about 320 kilometers northwest of Havana.

"This is where we decided9 to draw the battle lines," said John Rogner, the assistant director of the Illinois Department of Natural Resources.  "We have an electrical barrier in place that we are confident will keep them from moving en masse into the Great Lakes.  And then our job is to put out the brush fires so to speak.  The fish that, for one reason or another, that found their way past the barrier, we suppressed them and try to take them out of the system to keep them from establishing in Lake Michigan."

In June, a bighead Asian Carp was found above the electrical barrier about ten kilometers from Lake Michigan.  The discovery raised the level of concern that the invasive species was closer to Lake Michigan than previously10 thought.  But the Illinois Department of Natural Resources is confident their containment11 measures are working, as they have yet to find more Asian carp above the electric barrier.
 


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1 ecosystem Wq4xz     
n.生态系统
参考例句:
  • This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
  • We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。
2 ecosystems 94cb0e40a815bea1157ac8aab9a5380d     
n.生态系统( ecosystem的名词复数 )
参考例句:
  • There are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》
  • Madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样,从雨林到半荒漠等不一而足。 来自辞典例句
3 algae tK6yW     
n.水藻,海藻
参考例句:
  • Most algae live in water.多数藻类生长在水中。
  • Algae grow and spread quickly in the lake.湖中水藻滋蔓。
4 catfish 2OHzu     
n.鲶鱼
参考例句:
  • Huge catfish are skinned and dressed by hand.用手剥去巨鲇的皮并剖洗干净。
  • We gigged for catfish off the pier.我们在码头以鱼叉叉鲶鱼。
5 stun FhMyT     
vt.打昏,使昏迷,使震惊,使惊叹
参考例句:
  • When they told me she had gone missing I was totally stunned.他们告诉我她不见了时,我当时完全惊呆了。
  • Sam stood his ground and got a blow that stunned him.萨姆站在原地,被一下打昏了。
6 buffalo 1Sby4     
n.(北美)野牛;(亚洲)水牛
参考例句:
  • Asian buffalo isn't as wild as that of America's. 亚洲水牛比美洲水牛温顺些。
  • The boots are made of buffalo hide. 这双靴子是由水牛皮制成的。
7 undesirable zp0yb     
adj.不受欢迎的,不良的,不合意的,讨厌的;n.不受欢迎的人,不良分子
参考例句:
  • They are the undesirable elements among the employees.他们是雇员中的不良分子。
  • Certain chemicals can induce undesirable changes in the nervous system.有些化学物质能在神经系统中引起不良变化。
8 predator 11vza     
n.捕食其它动物的动物;捕食者
参考例句:
  • The final part of this chapter was devoted to a brief summary of predator species.本章最后部分简要总结了食肉动物。
  • Komodo dragon is the largest living lizard and a fearsome predator.科摩多龙是目前存在的最大蜥蜴,它是一种令人恐惧的捕食性动物。
9 decided lvqzZd     
adj.决定了的,坚决的;明显的,明确的
参考例句:
  • This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
  • There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。
10 previously bkzzzC     
adv.以前,先前(地)
参考例句:
  • The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
  • Let me digress for a moment and explain what had happened previously.让我岔开一会儿,解释原先发生了什么。
11 containment fZnyi     
n.阻止,遏制;容量
参考例句:
  • Your list might include such things as cost containment,quality,or customer satisfaction.你的清单上应列有诸如成本控制、产品质量、客户满意程度等内容。
  • Insularity and self-containment,it is argued,go hand in hand.他们争论说,心胸狭窄和自我封闭是并存的。
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TAG标签:   VOA标准英语  predator  predator
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