PrepTest 151, Section 3, Question 6
Watanabe: To protect the native kokanee salmon in(60 more words not shown)
Which one of the following(8 more words not shown)
- AEliminating a non-native(23 more words not shown)
- BWhen trying to(25 more words not shown)
- CThe number of(13 more words not shown)
- DNo non-native species(17 more words not shown)
- EWhen seeking to(29 more words not shown)
Reading the argument
Why would catching trout protect salmon? My first guess might be competition for food or space, but Watanabe gives a more direct reason: each mature trout eats about 250 mature kokanee a year. Removing some of those predators could help the salmon survive.
Lopez identifies another problem. The shrimp were introduced as food for the mature salmon, but they eat the plankton that the young salmon need. The attempted food source has become a competitor, and the young fish are starving.
What we’re looking for
Maybe both problems matter. Why should we eradicate the shrimp instead of allowing trout fishing? To support Lopez's preference, I'd initially look for a rule saying that losing the food supply is a more serious problem than being eaten by predators. We need something that gives the shrimp proposal priority, rather than merely showing that it could help.
Working the answers
- ACorrect
This uses a different distinction from my prediction: the shrimp were introduced, while the salmon and trout are native. The shrimp threaten the native salmon by eating the young salmon's food. A says removing a threatening non-native species is preferable to any other way of protecting the threatened native species.
That directly selects Lopez's proposal over trout fishing. We don't have to establish that the shrimp kill more salmon than the trout do. Under this rule, their non-native status and threat to a native species are enough to give eradication priority.
- B
We don't know which proposal would produce the quickest results. The rule would require that comparison before it could favor Lopez. Protecting the food supply may be relevant to protecting the salmon, but B doesn't show that shrimp eradication wins under its own speed criterion.
- C
Eradicating the shrimp would remove a species from the lake. A rule against reducing the number of species doesn't favor that proposal; it gives us a reason to look for an alternative that preserves the shrimp. Lopez is defending eradication, not simply preserving every species already present.
- D
The shrimp have already been introduced. This principle tells us what to consider before adding a non-native species, not what to do once its harmful effects appear. Even if the original introduction violated D, we still need a reason to prefer eradication over trout fishing now.
- E
Which salmon are in their prime reproductive stage? We aren't told. Watanabe's proposal protects mature fish from predators, while Lopez's protects young fish from starvation. E doesn't establish that protecting the young fish has the priority it describes. It could not select Lopez's policy without more information about the relevant life stage.
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