亞洲的一種蛇頭魚(snakehead fish)被引入北美，對北美的生態系統產生威脅。有幾種方法可以阻止蛇頭魚在北美的擴張。

　　第一種方法是：制定法律。魚市的人經常把賣剩下的魚倒入北美的河流湖泊中。只要制定法律限制這種行為便可阻止非本土的蛇頭魚對北美的生態環境造成危害。

　　第二種方法是：讓北美的人了解到蛇頭魚是可以食用的。在亞洲，蛇頭魚是餐桌上的一道美食。而在北美，幾乎沒人食用蛇頭魚。所以，只要讓北美的人了解到蛇頭魚是一道美食，漁民們便會開始大量捕殺它們，最終減少它們的數量。

　　第三種方法是：毒死那河流里的蛇頭魚。雖然這些有毒物質不僅僅會毒死蛇頭魚還會毒死本土的一些魚種，但是可以重新在這些水域養殖本土的魚種。

　　聽力主要觀點提取：

　　閱讀中提到的每一種方法都不能保護美國的生態系統。

　　制定法律阻止人為將蛇頭魚引入北美并沒用。因為蛇頭魚可以完全依靠自己從一個河流轉移到另一條河流。

　　讓漁民知道蛇頭魚是一道美食會適得其反。因為，當漁民知道賣蛇頭魚可以掙錢，他們會想法設法在更多水域養殖這種魚，以便能夠捕獲更多數量。所以，蛇頭魚的數量不會下降。

　　毒死蛇頭魚然后再重新養殖本土魚種不是一個好主意。因為有毒物質不僅僅會毒死河流里的魚，還會毒死一些小的生物，如昆蟲和兩棲動物(amphibian)。這些生物一旦被毒死就無法恢復。然而，很多本土的魚種以這些生物為食。所以，這種方法會導致之后重新養殖在湖泊里的本土魚沒有食物，數量會下降。

　　最新托福寫作范文：

　　The writer puts forward three methods to stopping the spread of snakeheads in North America. Nevertheless, the professor demonstrates that none of the methods are likely to protect North America ecosystem.

　　First, in terms of making it illegal to transport and release snakeheads, the professor states that the snakeheads can spread to new waterways by themselves even without human’s transporting them. The reason is that snakeheads are able to live and move on land as long as they remain moist. So they can stay wet to reach a new lake or river.

　　Second, different from the belief in the reading that educating the fishers about snakeheads would reduce snakeheads’ population, the professor points out that it could end up with spreading snakeheads not reducing their number. When the fishers see the benefit to catch snakeheads, they would intentionally to introduce them to other lakes or rivers, even it is illegal. By dong this, they could catch more snakeheads and earn more money.

　　Finally, the professor contradicts the reading by saying that poisoning and restocking lakes or ponds is not a good idea. That’s because poisoning not only just kill snakeheads and other fishes, but also kill many small organisms, such as insects and amphibians which are the food source of native fishes. What’s more, these small organisms can not recover after being poisoned. As a result, it is not easy to restore the ecosystem by using poisoning.

      以上就是本文的全部內容，更多精彩請隨時關注新東方長春學校官網。

相關推薦

長春新東方托福課程導航

長春新東方托福課程

長春新東方托福課程表

長春新東方托福在線咨詢