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The reading passage suggests that people cannot stop the spread of zebra mussels and there will be threat to fish population. However, in the lecture, the professor argues that there are ways to control the population of zebra mussels and the threat brought is not clear.
First of all, the professor argues against the reading’s statement that the history of the spread of zebra mussels by human transportation makes the increase of their number unstoppable. The professor supports this idea by pointing out that this might be true in the past when people did not have knowledge about how to control zebra mussel population. Now there are effective ways to stop the spread. The professor explains that zebra mussels travel in fresh ballast water in the ship from Europe and the water is emptied out in North America. In order to control the spread, the ship can empty the water while it is still in the ocean and fill the ship with ocean water, and as a result, the salt water will kill the mussels.
Besides, the reading claims that zebra mussels are able to dominate a new habitat once they are introduced. On the contrary, the professor points out that in the beginning, zebra mussels might not have predators. However, the birds will notice that there is a new source of food available, and they will switch from whatever they were eating to eating zebra mussels. Moreover, the birds are able to eat a lot of zebra mussels. Therefore, it is unlikely that zebra mussels will dominate the new habitat.
Finally, the reading passage demonstrates that the spread of zebra mussels will lead to the decrease of the number of fish. The lecture, however, asserts while zebra mussels may exert negative influences on some of the freshwater fish species, they have positive impacts on other fish. For example, they generate nutrition that is eaten by bottom-feeding fish. That is to say, even though the population of plankton-eating fish will decrease, the number of bottom-feeding fish may increase.