Osprey Prey

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Seattle's osprey population has been declining in recent years, primarily because of hunting, both legal and illegal. Osprey prey heavily on salmon, a fish that is prized as food by the coastal population, who had hoped at least that the decline in the osprey population would lead to an increase in salmon for human consumption. Yet the naturally occurring population of salmon has also declined, even though the annual number caught for human consumption has not increased.

Which of the following, if true, most helps to explain the decline in the population of the salmon?

The decline in the osprey population has meant that fishers can work in some parts of lakes and rivers that were formerly too congested.

Over the last few years, Seattle's commercial fishing enterprises have increased the number of fishing boats they use.

A primary predator of salmon is the American eel, on which osprey also prey.

Many Seattle residents who hunt osprey do so because of the high market price of osprey plumage, not because of the threat osprey pose to the natural salmon population.

In neighboring stretches of coastline near Seattle, osprey are endangered as a result of extensive hunting.

Review: Osprey Prey

Explanation

Reading the question: did you start with the stem on this question? Either way, we discover when we get to the stem that we have to "explain" on this question, just as we did in "Alternative Plants." "Explain" questions have similar features:

The mystery needing explaining has two parts.
The correct answer...
- ...usually addresses both parts of the mystery; and
- ...never contradicts the facts in the prompt.

Creating a filter: in this question, the two parts of the contradiction are delineated by the word "yet." Most "explain" questions have such a division word in the prompt. On one side of the "yet," 1) the osprey have declined. On the other side: 2) their predator, osprey, haven't declined (and we aren't fishing them any more than before). Our filter is to look for an answer choice that addresses both 1) and 2) without contradicting either.

Applying this filter, we can turn to the answers: Choices (A) and (B) irrelevant, because we know fishing isn't the explanation. Choice (C) looks relevant. We'll come back to it. Choice (D) is irrelevant; who cares why we hunt osprey? (E) is similarly irrelevant. Choice (C) is a great explanation. It presents an overlooked effect of the lower number of ospreys. Eels are more populous than ever and gobbling up the salmon, even though there are fewer osprey. The correct answer is (C).

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Osprey Prey