Q16 - Researchers in South Australia estimate

[opulence2001]

Could someone please break down this question and explain why E is the correct answer and the rest are wrong?

[giladedelman]

Thanks for posting!

The researchers conclude that the shark population around South Australia must be around what it was back in 1973, because the "catch per unit effort" has remained the same since then. In other words, because people are catching sharks at around the same rate, there must be the same number of sharks available.

If you're not seeing the gap in that logic, consider this example:

"In 2009, Gilad got 100 hits as a member of the Yankees. In 2010, he also got 100 hits. So he must have had the same number of at-bats in both seasons."

Well, wait a minute -- what about my batting average? What if I got a lot worse between 2009 and 2010? Then it would stand to reason that it took me many more at-bats to get to 100 hits than it did in the previous season.

The shark argument makes the same mistake. Just because people are catching the same number of sharks per attempt doesn't mean the shark population hasn't changed. Maybe it has changed, but the fishermen have gotten better or worse at catching them!

That's why (E) weakens the argument -- it challenges the assumption that the ability to catch the sharks is unchanged. If sharkfishing boats have been using sophisticated shark-finding technology that increases their accuracy, but they're still catching the same number of sharks, then the shark population must actually have decreased; otherwise, we'd expect them to be catching more sharks!

(A) is irrelevant because the argument explicitly limits itself to the waters around South Australia.

(B) is out of scope as soon as it mentions the "most profitable" sharks. Who cares?

(C) is tempting, but this doesn't help us figure out whether the shark population has changed since 1973. Was "incident mortality" a threat back then, too? We don't know.

(D) is out of scope, first in its mention of quotas and, second, because the argument defines CPUE specifically in terms of the number of sharks caught. So that's what we care about.

Does that clear this one up for you?

[opulence2001]

Ookaayy!! So essentially... if your are getting better at doing something (ie. catching sharks) and the amount you catch is the same, then you should be questioning if the amount there is to catch has changed!!!

I am up to speed.

Thank-you!

[goriano]

I noticed that all the answers except for (E) don't mention time frame so all these new "conditions" could very well apply to pre and post 1973. I noticed you used this logic to eliminate (C), and was wondering whether that strategy could be used to eliminate (A), (B), and (D) as well.

[goriano]

The shark argument makes the same mistake. Just because people are catching the same number of sharks per attempt doesn't mean the shark population hasn't changed. Maybe it has changed, but the fishermen have gotten better or worse at catching them!

In addition to having the LSAT Geeks answer my first post for this question, I'd like clarification on this too!

How is it possible that you can have people catching the same # of sharks per attempt but also have fisherman getting better or worse at catching them? It seems like a contradiction.

[giladedelman]

In response to your first question: Absolutely!!! In fact, that's probably your best bet for getting to the right answer since (E) is not at all obvious at first glance. By noticing that four of the choices have nothing to do with the change over time, you can be pretty confident that it has to be (E) even if you're not really sure why.

As for your second question: no, it's not a contradiction, because maybe the amount of available sharks, i.e. the shark population, has declined. So if my ability level had stayed the same, I'd be catching fewer sharks, but since I've gotten better or adopted new technology or whatever, I can catch the same number even though the population has decreased. If the population of sharks had stayed the same, then we'd expect me to catch more sharks as I got better at shark fishin'.

You dig?

[dean.won]

For E to be correct dont we have to assume the year is post 1980??
I wanted to choose E but i couldnt confidently pick it cuz we werent told what year it is currently in the argument...

[griffin.811]

The answer says "since 1980.." This means the passage must have been written after 1980.

Imagine I tried to get published an article today that said "Since 2017, the worldwide economy has flourished." It would be hard to find a publication that would publish this.

I dont think LSAT writers want us to question the truth of the answer choices in that sense.

[ManhattanPrepLSAT1]

Good point griffin.811!

How literal do the test writers want us to be? I think the answer is you have to give the test-writer some "everyday common sense." Otherwise, they'd have to spell out every single last point and the extra "clarity" would only be confusing and awkward to read.

[redcobra21]

Thanks for the great explanations, Gilad and Matt! Really helped a lot.

I just had one more clarificaition question if you guys got the chance.

For (E), it seemed like it required an additional assumption that I wasn't really sure could be warranted in the first place. After all, just because these fishermen might have a great tool that allows them to better locate sharks doesn't necessarily mean that they will do so (some other quality might negate the new advantages). Are we allowed to assume that the new equipment can basically be translated to them actually catching more sharks?

Also, when I read the question, my eye was immediately drawn to how they were trying to draw a general conclusion about the population of sharks from just one source (ie data from commercial shark fishing boats). Would (C) have been correct if it had been the same answer choice but had simply added something like "since 1980" to the beginning?

Thanks in advance!

[WaltGrace1983]

Thanks for the great explanations, Gilad and Matt! Really helped a lot.

I just had one more clarificaition question if you guys got the chance.

For (E), it seemed like it required an additional assumption that I wasn't really sure could be warranted in the first place. After all, just because these fishermen might have a great tool that allows them to better locate sharks doesn't necessarily mean that they will do so (some other quality might negate the new advantages). Are we allowed to assume that the new equipment can basically be translated to them actually catching more sharks?

Also, when I read the question, my eye was immediately drawn to how they were trying to draw a general conclusion about the population of sharks from just one source (ie data from commercial shark fishing boats). Would (C) have been correct if it had been the same answer choice but had simply added something like "since 1980" to the beginning?

Thanks in advance!

For the first question, I would personally think so. It says that "shark-fishing boats have used sophisticated electronic equipment..." which sounds to me like it is a reasonable assumption to think that this actually translated into more shark-catching. If not, well it is clearly the BEST answer anyway.

If you added that, "since 1980 there has been a significant threat to the shark population..." I think that would be an okay weakener. I guess it would imply that there ARE more sharks BUT then again it also still shows that these "additional" sharks ARE getting taken by other people, thus equaling out the population anyway. (E) would still be a better answer because it avoids this whole issue of what actually constitutes "population."

[AnnaT620]

I think I'm still not clear on how C doesn't weaken the argument? Surely if there is a significant threat to shark populations, in addition to commercial shark fishing, is "incidental mortality" that results from catching sharks in nets intended for other fish - then there can't be the same levels of population of that species in the waters as in 1973.

I read E and thought that was out of scope - just because they got new equipment, they're still catching the same number of sharks (as set out in the premise, which we're meant to accept as true?).

Sorry for the many questions. Really appreciate all the help.

Thanks so much!

[Laura Damone]

Hi!

Curious if you read Gilad's post further up the chain. He's an instructor and his explanation of C is spot on: "incident mortality" is a threat, but it isn't necessarily a new threat. It may well be that this has always been a threat, in 1973 and today. Since the threat hasn't necessarily changed, we can't conclude that it's impacting shark population differently. Therefore, it doesn't weaken the argument that population has remained constant.

E on the other hand establishes a difference: we have better equipment now than we did then. If that's the case, the fact that we're catching the same number of sharks doesn't necessarily mean there are the same number of sharks in the water. It could be that there are fewer sharks and we're just better at catching them.

Consider this analogy:
I went fishing for goldfish in my neighbors pond (silently, under cover of darkness!) 2 weeks ago, and I went fishing for goldfish there again today. I caught 2 goldfish both times. Therefore, there were the same number of goldfish in the pond both times.

Hmm...seems suspicious, right? Now, what if I told you that 2 weeks ago I went with a pole and line, and today I went with a giant net. That would REALLY weaken that argument, right? Because I could catch way more fish with the net than the pole and line. So, if I only got 2 measly fish with my giant net, that probably means there are FEWER fish in the pond now than there were then.

Hope this helps!

One more thing - we LOVE to answer student posts. That's why we do this! But there is a LOT of traffic on the forum right now and we have to make sure that we spread the love around and answer some posts from each of our students. Are there particular posts of yours that you're particularly invested in getting answered? If so, you could send me a private message and I can make sure to prioritize those! ldamone@manhattanprep.com.

Sincerely,
Laura - LSAT content and curriculum lead