Please grade my GRE essay based on an argument

[Grewal]

Recent incursions by deep-sea fishermen into the habitat of the Madagascan shrimp have led to a significant reduction in the species population. With the breeding season fast approaching, the number of shrimp should soon begin to increase. Nonetheless, the population should not return to the levels before the fishing boats arrived. Because this trend is expected to continue over the next several years, the Madagascan shrimp will quickly become an endangered species.

Write a response in which you discuss what specific evidence is needed to evaluate the argument and explain how the evidence would weaken or strengthen the argument.

 

The argument doesn't seem to be coherent, making several assumptions without reasoning through the various questions coming to mind. Firstly, it doesn't make clear as to why the species population fell sharply, merely saying that recent incursions by deep-sea fishermen into the habitat of Madagascan shrimp led to the drop in population.

The argument doesn't say whether the fishermen caught shrimp or fishes that the shrimp fed on. We just don't know what caused the population drop. There could be other reasons for this that may not be linked to the fishermen's incursions in the area. For instance, global warming could have caused the water temperature to rise, making the area unsuitable for shrimps or there could have been an environmental catastrophe such as a big oil spill that killed the shrimp.

Secondly, the argument says that shrimp population should not return to levels before the fishing boats arrived, adding that this may result in Madagascan shrimp becoming an endangered species. This statement isn't logically sound. Even if we assume that the shrimp's population declined due to the fishermen, what's to say the species will not become extinct if the population doesn't return to its previous levels. The deep-sea fishermen can still catch the remaining shrimp, and thereby reducing their number bit by bit every year until they go extinct.

Thirdly, if we assume that the shrimp's number doesn't reach levels before the fishermen had arrived, they can still catch the shrimp and reduce their population drastically.

Further, if the shrimps were not to increase in population and the fishermen were not to catch them, how do we know that their numbers will increase, not knowing how many times their breeding season occurs in a year and how much time do they take to muliply. These are all gaping holes in the argument. Unless these things are made clear we can't reach the conclusion that the argument has reached.

Also, we are also not told how many times the fishermen come to the area. Do they come once in a year, six months, three months or every month?

Before making any more deductions from this argument, we need to be told what is the population of shrimp in the region and how many shrimps have the fishermen supposedly caught. Without these numbers, the argument comes across as vague. Only when we know how fast do the shrimp multiply and how many are caught can we make projections about the extinction of the shrimps.

These are some of the assumptions made in the argument and without answering the abovementioned specific questions, we can't reach this conclusion. To be cogent, the author needs to think through the argument.