LSAT 16 - Section 2 - Question 16

We should know this is a weakening question, since it asks us: Which one of the following, if true, most seriously weakens the argument?

This is a 5 star question, and the stimulus throws a lot of stuff to remember at us. The first sentence tells us about a “catch per unit effort” (CPUE) that is used to monitor shark populations in local waters. We are then given a definition of what the CPUE is: it is the number of an individual species of shark that shark-fishing boats catch per hour for each kilometer of net in the water. We’re only two sentences in and we’ve already been given an information overload; South Australia, sharks, catch per unit effort, commercial shark-fishing boats, per hour per km of net. Similar to how low-res summaries are helpful on RC, on dense LR passages it’s helpful to try and translate what’s going on into your own words. Something like “Shark population changes are monitored by how many of a species are caught considering the time and size of net used.”

All of this information so far has just been context on what a CPUE is. Now we are told that there a species of shark whose CPUE has remained constant since 1973. From this the author concludes that the population of the shark species has remained constant since 1973. The major assumption of this argument is that the CPUE of a shark species is an accurate and consistent measure of its actual population changes. While there is always a lot of different ways to weaken an argument, we should expect that this assumption might play a role. An answer that undermines the CPUE’s accuracy and consistency will be a good answer for this question. Let’s see what the answer choices have in store for us:

Answer Choice (A) Always stay anchored in the conclusion. The conclusion we want to weaken specifically specifies that we are interested in the population of the species in the waters around South Australia. Whether or not it is found in other parts of the world is irrelevant.

Answer Choice (B) This might be an appealing answer if your eyes light up at seeing profitable, and you infer that this answer undermines the CPUE because people will only hunt where there are profitable sharks, and maybe the shark species isn’t profitable. The problem is that we don’t know if the species is profitable, and even if it wasn’t profitable we only know that profitable sharks tend to stay in the same spots. Maybe our species isn’t profitable but it is widely dispersed so that it gets caught in the profitable hunting areas. We just don’t have enough information for this answer to weaken the argument.

Answer Choice (C) Interesting! But this answer does nothing to undermine the argument that the CPUE is an accurate indicator of the species real population changes. Even if these nets kill lots of sharks, they still catch them so that we can compare how many are being caught per hour for each kilometer of net.

Answer Choice (D) Again, we just don’t get any information here that can weaken our CPUE is accurate argument. You might want to infer that this would encourage shark-fishers to catch higher numbers of smaller sharks, but that doesn’t affect the CPUE’s accuracy as an indicator of population changes.

Correct Answer Choice (E) What this answer does is give us a reason to believe shark-fishers should be catching a larger portion of shark populations than they did in 1973. If a new device is introduced that should mean higher rates of capture, but the CPUE stays the same, it suggests that the actual population has declined without the CPUE recognizing it. If the population was 20 before but the hunting technology only allowed 1 out of every 10 to be caught, and the population next year declined to 10 but the new device increased the capture rate to 2 out of every 10, the CPUE would stay the same while the population fell by 50%!