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Contrary to what you just read, there are ways to control the zebra mussel's spread.
与你们刚刚所阅读的相反，有许多方法来控制斑马贻贝的传播。
What's more, it is not so clear that the mussel is a serious threat to fish populations.
而且，也没有明确的说法贻贝对鱼类来说是一个严重的威胁。
True, the spread of zebra mussels couldn't be controlled in the past, but that's because people didn't have enough knowledge.
是的，斑马贻贝的传播在过去不能被控制，但那是因为人们对其了解不够。
In fact, there are effective ways to stop ships from carrying the mussels to new locations.
事实上，有一些有效的方法来防止船舶把贻贝带到新的地方。
Here's an example. The way zebra mussels usually travel across the ocean
这里有一例。斑马贻贝在海洋中穿行常用的方法是，
is that a ship takes on some fresh "ballast water" in Europe and then empties that water into American waterways when it arrives.
船舶在欧洲装上一些新鲜的“压舱水”，然后在到达美国时把这个说倒入其航道。
Full of zebra mussels, but the ship can be required to empty out the freshwater and refill with ocean water while still out in the ocean.
水里满是斑马贻贝，但是可以要求该船仍在海洋中时把淡水倒掉重新装上海水。
Salt water will kill the mussels.
海水能杀死贻贝。
Second, it's true that zebra mussels often don't have predators in their new habitats, but that's only in the beginning.
第二，斑马贻贝在新的栖息地里没有掠食者这是真的，但，仅仅是在开始的时候。
What's been happening in Europe is that local aquatic birds sooner or later notice there's a new food source around and change their habits to exploit it.
在欧洲已经发生的是，当地的水鸟迟早会发现周围有一个新的食物来源并且改变它们的习惯来捕食贻贝。
They switch from whatever they were eating before to eating zebra mussels.
不管它们以前吃什么，他们转而吃斑马贻贝。
And birds can eat a lot of mussels.
鸟儿们能吃掉很多的贻贝。
So zebra mussels aren't so likely to dominate their new habitats after all.
所以，斑马贻贝终究不太可能占领新的栖息地。
Finally, even in habitats where zebra mussels become dominant, is the overall fish population likely to decrease?
最后，即使在斑马贻贝占领者的栖息地里，全体鱼类的数量有可能减少吗？
It's true that zebra mussels may have a negative impact on fish that eat plankton.
当然，斑马贻贝可能对那些吃浮游生物的鱼类着负面影响。
But on other fish, they can have a positive impact.
但对其他鱼类，他们会有一个正面的影响。
For example, the mussels generate nutrients that are eaten by fish that feed near the bottom of the lake or river.
比如，贻贝能产生营养物质，供在靠近湖底或者河底觅食的鱼类食用。
So bottom-feeding fish populations may increase, even if plankton-eating fish population (decrease).
所以，即使吃浮游生物的鱼类数量会减少，吃残羹剩餐的鱼类数量可能会增加。
