Zebra Mussels - Shellfish

Regarding the reading, the number of the Zebra mussels , a freshwater shellfish, cannot be stopped due to three reasons. In contrast the professor believes that this could be control under special circumstances, so he refuted all the author's reasons based on three concrete pieces of evidences.

First, that the ships and the human transportation got the number of Zebra to increase, based on what the reading claims, is refuted by the professor. He states that this happened once before because of the lack of people's knowledge. The fact of the matter is that since the ships carry the huge number of the Zebra within the water existed in their cargo, Should they refill their cargo, they would use salty water in order to kill Zebra.

Second, the reading states that the Zebra mussels are predominant in new habitat. Quite the reverse, the professor believes that the Zebra is recognized by special kind of bird which searching for new source of food. Therefore there is no chance for the Zebra to be a dominant species in all habitats after all.

Third, according to the reading, the more the Zebra, the less the overall fish population. The professor casts doubt on this issue by saying that this matter is just related to some kinds of fish such as Plankton. To illustrate more, while the Zebra kills plankton, it is useful for other kinds of fishes either. In fact, the Zebra produces nutrients which feed some other groups of fishes that live on the bottom of rivers.