#16 - Researchers in South Australia estimate changes in

[8scn]

Why is D not correct? For D, my reasoning is: limiting the tonnage means that fewer numbers of heavier sharks can be caught as opposed to greater numbers of lighter sharks. So this would be a way for the population of sharks to differ from 1973 levels.

[Adam Tyson]

The question deals with a simple numbers game on its face - the number of sharks caught per hour hasn't changed, and since that number tells us the size of the shark population, we conclude that the population hasn't changed. To weaken that, we want to show that the population could be lower or higher than before and yet still result in the same number of sharks caught.

E suggests that the boats should be getting a greater percentage of the shark population than they used to because of their better technology. If the numbers are the same, but the percentage they represent is now higher, that means the shark population has actually shrunk! Looked at another way, if E is true, you would expect more sharks to be caught, and so the constant number represents a paradox. You can solve that paradox by showing that the population of sharks is smaller than it was.

D tells us about quotas and tonnage, but regardless of how much they weigh we are still catching the same number as before, and the stimulus tells us simply that the number caught indicates the size of the population. We might be catching fat sharks or skinny sharks, but we might have been doing that all along - either way, the numbers have remained constant.

Adam Tyson
PowerScore LSAT Instructor

[karen_k]

Hi,

I am having trouble understanding why E is the correct answer. Wouldn't being able to locate sharks with greater accuracy lead to more of them being caught and therefore the CPUE not remaining constant? Is that in itself the reason it weakens the argument? When I first read the stimulus, I thought the correct answer would show a difference in the population level and I ended up choosing C because I thought it gave a possible reason for the shark population to be lower, not constant. Any clarification would be greatly appreciated!

[Nikki Siclunov]

Hi Karen,

Let's see what we know: you're catching the same number of sharks now as you did back in 1973, and conclude that the shark population must have remained fairly constant. This is not a good argument. What if, as answer choice (E) suggests, you are a lot better at finding the sharks now than you were back in 1973? You're still catching the same number of sharks, but it's entirely possible that there are a lot fewer sharks out there to catch! You're just better at finding them.

At its core, this is a causal argument: the author believes that the reason why your CPUE has remained constant is because the shark population has remained constant. After all, CPUE is a marker of how many fish you have in that area:

constant shark population (cause) constant CPUE (effect)

If answer choice (E) is true, you're looking at a different cause. There could be a lot fewer sharks out there, but if you're a lot better at finding them then maybe that's why you're just as successful as you were in 1973

Answer choice (C) says sharks might be getting caught in nets meant for other fish. This would only be relevant if you want to explain why the shark population is dwindling. You don't know if it is. You also don't know if this behavior is anything new: what if sharks have always had the habit of getting caught in nets meant for other fish?

Hope this helps!

[karen_k]

Thank you, Nikki!

[OneSeventy2019]

Powerscore,

I was able to chose answer choice E correctly based on my pre-phrase that, "now better at catching sharks" which matched closely with answer choice E. My only hesitation to choosing answer choice E was that the argument mentioned that the CPUE has not changed since 1973 and the new technology was not adopted until 1980.

Correct me if I am wrong, but I feel that typically when I have encountered a question like this, LSAT writers always say something like, "...and in 1986, the CPUE was at same" or "the CPUE did not change from 1973-1986". Basically, what they are doing is 'grounding' us making sure that we (as in, the point in time in which we are evaluating the argument) are in or past the year 1980.

I understand that this test was administered in the 1990s so perhaps they are just assuming that we all know that the year (in the argument) is past 1980. But if the year was 1978, then choice E would actually not weaken the argument at all. Maybe it has something to do with this being an older test but I feel like this question is unique in that most other LSAT questions don't require testers to use their outside knowledge of the test administration date to answer the question.

Let me know if this is a ridiculous point to raise, but just trying to get into the LSAT writers head a bit more..

[Adam Tyson]

Some outside knowledge is assumed on the LSAT, OneSeventy2019. The test is designed to be administered to people who either have a Bachelor's degree or are just about to complete one, and so they assume you have a lot of knowledge. For example, they assume you can handle all the vocabulary on the test, that you know what an average is and how it is calculated, that you understand that there is some relationship between supply and demand, and that if the sun is shining then it is probably daytime. They expect you to know that predators are part of the environmental conditions faced by prey species, that animals need food and water and air to survive, and that nutrition ingested by a nursing mother can be passed through their milk to their offspring. There is a LOT of outside information that they consider fair to expect us to know, and that is critically important to understanding the arguments and RC passages and even the game scenarios.

And yes, they assume you know approximately what date it is! It is completely fair for them to ask this question on a test first administered in 1995 that references past dates like 1980, and to expect that you know that it is in the past.