They switch from whatever they were eating before to eating zebra mussels.

他们从以前吃的任何东西转变为吃斑马贻贝。

Often this happens unintentionally, as when the zebra mussel was accidentally brought to Lake Erie by cargo ships.

这通常是无意中发生的，例如斑马贻贝被货船意外带到伊利湖。

So zebra mussels aren't so likely to dominate their new habitats after all.

所以斑马贻贝不太可能主宰它们的新栖息地。

It's true that zebra mussels may have a negative impact on fish that eat plankton.

的确，斑马贻贝可能会对以浮游生物为食的鱼类产生负面影响。

Finally, even in habitats where zebra mussels become dominant, is the overall fish population likely to decrease.

最后，即使在斑马贻贝占主导地位的栖息地， 鱼类总数也可能减少。

True, the spread of zebra mussels couldn't be controlled in the past, but that's because people didn't have enough knowledge.

诚然，斑马贻贝的蔓延在过去是无法控制的， 但那是因为人们没有足够的知识。

Second, it's true that zebra mussels often don't have predators in their new habitats, but that's only in the beginning.

其次，斑马贻贝在新栖息地通常没有捕食者， 这是事实，但这只是开始。

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.

满是斑马贻贝， 但船可能需要清空淡水并在仍在海中时重新装满海水。

The way zebra mussels usually travel across the ocean is that a ship takes on some fresh " ballast water" in Europe and then empties that water into American waterways when it arrives.

斑马贻贝通常穿越海洋的方式是， 一艘船在欧洲装载一些新鲜的“压载水” ，然后在到达美国时将这些水排入美国水道。