LSAT 144 | Section 2 | Logical Reasoning: Q9

LR Question 9 Explanation

QUESTION TEXT: Two lakes in the Pawpaw mountains, Quapaw…

QUESTION TYPE: Weaken

CONCLUSION: The fishing ban probably was the reason that Quapaw lake’s fish population has recovered.

REASONING: Both Quapaw and Highwater lakes have had fish population declines. Quapaw lake had a fishing moratorium. After that, the fish population there recovered. Highwater had no moratorium, and its population continued to decline.

ANALYSIS: This argument “feels” correct. Our brains have a very difficult time with correlations – we think they are causation.

But what if there was practically no fishing at Quapaw even before the moratorium? What if the moratorium wasn’t enforced?

There is a correlation between the moratorium and the recovery, but we don’t actually have evidence that the moratorium caused the recovery.

Note that Highwater lake plays very little role in the argument. The only thing Highwater shows is that Quapaw isn’t following a global or regional trend. The continuing decline at Highwater rules out, for example, human restocking of all regional lakes as a reason for the increase. Highwater otherwise plays no role.

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1. So? This might indicate that acid rain caused the decline at Highwater, but this isn’t relevant to Quapaw. The argument never said fishing was the cause of the decline in both cases.
2. CORRECT. This devastates the argument. The fishing ban can’t have been the cause if there was no fishing anyway.
3. So? Relative lake size doesn’t matter. It’s not as if large lakes have fishing population declines merely because they’re large.
4. So? We don’t know anything about those lakes. Maybe those lakes never had declines in the first place.
5. When did this happen? This could have been 80 years ago. In any case, the question is only asking about fish numbers, not fish species diversity.