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Dear [url=https://gmatclub.com:443/forum/memberlist.php?mode=viewprofile&un=GMATNinja%5D%5Bb%5DGMATNinja%5B/b%5D%5B/url%5D
I spent a lot on this question and still I think A is contradicting the conclusion!
in conclusion illegal harvesting in culprit but in A it is saying its saying the harvesting by illegal was not so extensive!
would you pls clarify it?
I do appreciate in advance for your time
It's important to read the whole sentence! Look at (A) again:

Quote:
(A) The illegal lobster harvesting was not so extensive that the population of catchable lobsters in Belukia’s territorial waters had sharply declined by 1996.
This isn't saying that the illegal harvesting wasn't extensive. It's saying that it wasn't extensive enough to cause a sharp decrease in the number of catchable lobsters!

That's a big difference. If I say "Tim didn't eat so much that he exploded", I'm not saying that Tim didn't eat a lot. I'm saying that there aren't chunks of Tim splattered on the sofa.

Once you take into account (A) in its entirety, you'll see that it has to be true. Imagine that it's typically the case that 10,000 lobster are caught legally. But then one year, when illegal fishing is up, only 1,000 are caught legally. If we're going to conclude that 9,000 more lobsters were caught illegally that year, we're assuming that the total is pretty much constant. In other words, the increase in illegal fishing perfectly offsets the decreased in legal fishing.

But if the illegal fishing caused the overall numbers to plummet, well, there's no longer any reason to believe that an increase in illegal fishing would fully offset the decrease in legal fishing.

So we're assuming the illegal fishing wasn’t so overwhelming that it caused the overall fishing numbers to plummet, and that's exactly what (A) is saying.

I hope that clears things up!
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I think the question is wrong.
"no reduction in the level of legal lobster fishing activity, the local catch was 9,000 tons below pre-1992 levels." is badly written.

It should be that no reduction in the level of total lobster fishing activity, the local legal catch was 9,000 tons below pre-1992 levels. Thus, it is therefore highly likely that the outlaw fishing boats fish about 9,000 tons of lobster illegally that year.
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Emily1122
I think the question is wrong.
"no reduction in the level of legal lobster fishing activity, the local catch was 9,000 tons below pre-1992 levels." is badly written.

It should be that no reduction in the level of total lobster fishing activity, the local legal catch was 9,000 tons below pre-1992 levels. Thus, it is therefore highly likely that the outlaw fishing boats fish about 9,000 tons of lobster illegally that year.

Not correct.

"no reduction in the level of legal lobster fishing activity" means "same number of legal boats were going on for the same number of hours to catch," but still they were catching fewer lobsters. Essentially it says that the legal EFFORT to catch was the same as previous years but fewer were getting caught. It is eliminating the possibility that fewer legal boats are going int o catch lobsters and that is why fewer lobsters are getting caught.

The level of illegal lobster fishing activity is unknown.
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Hey there! Let's tackle this assumption question together - I can see why this one might be tricky at first glance.

Breaking Down the Argument:
The author is basically saying: "Legal catches dropped by 9,000 tons, and since legal fishing activity stayed the same, those 9,000 tons must have been caught by the illegal boats instead."

Let's think about this step-by-step:

Step 1: Understand the Math
- Before 1992: Legal boats caught, say, 20,000 tons
- In 1996: Legal boats caught 11,000 tons (9,000 tons less)
- Legal fishing effort: Stayed the same
- Author's conclusion: Illegal boats took those missing 9,000 tons

Step 2: Find the Hidden Assumption
Here's what you need to see - the author assumes those 9,000 tons of lobsters still exist to be caught. But what if the illegal fishing was so intense that it actually destroyed the lobster population?

Think about it this way: If overfishing depleted the total lobster population, then legal boats catching 9,000 tons less doesn't mean illegal boats caught 9,000 tons more. It could mean there are simply 9,000 tons fewer lobsters in the ocean!

Step 3: Test the Answer Choices
Notice how choice (A) directly addresses this: "The illegal lobster harvesting was not so extensive that the population of catchable lobsters... had sharply declined."

This is exactly what the argument needs to assume! Without this assumption, the missing 9,000 tons could represent dead lobsters rather than illegally caught ones.

The other choices? They're distractors:
- (B) talks about individual boat efficiency - irrelevant to the total
- (C) compares legal vs illegal capacity - not what we're measuring
- (D) seems tempting but the argument is about the difference, not absolute values

Answer: (A)

For the complete framework on tackling assumption questions and discovering the systematic approach to identify these hidden gaps, you can check out the step-by-step solution on Neuron by e-GMAT. You'll learn how to quickly spot alternative explanations in similar problems and master the negation test technique. You can also explore other GMAT official questions with detailed solutions on Neuron for structured practice.
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This is a rather weird logic in my view and i cant grasp what’s happening at all.

How is it possible to say that the illegal fisher must have caught 9000 instead of the legal fishers if they dont assume all of the catchable lobsters are caught??
Shouldn’t this be the real assumption here?

Even if we assume the population of lobster did not decline significantly, may be the illegal fisher still didn’t catch the other 9000 or may be higher or lesser we dont know because we are yet to assume all catchable lobsters are caught, so why does this assumption matters??

And if we dont assume this and the population of lobster declined significantly, why cant we still assume the illegal party still was able to catch 9000?

For example if there were 100,000 lobster in 1996 and in 1992 declined significantly to 30,000, the number of the lobster caught by legal fishers would have been decreasing over the years which is in line with the story and 9000 less in 1996. So may be from 20000 to 11,000. There are still 19000 catchable lobsters left so it’s still possible that the illegal fishers caught the 9,000 instead. Unless if choice A states that the remaining catchable lobster is significantly lowered to below 9000+number they caught in 1996, then i dont see how negating this option really destroy conclusion.

In my view if it’s significantly lowered then all the more reason both fishers were able to caught all catchable lobsters which would make sense how they know how many the other party got.
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This is a rather weird logic in my view and i cant grasp what’s happening at all.

How is it possible to say that the illegal fisher must have caught 9000 instead of the legal fishers if they dont assume all of the catchable lobsters are caught??
Shouldn’t this be the real assumption here?

Even if we assume the population of lobster did not decline significantly, may be the illegal fisher still didn’t catch the other 9000 or may be higher or lesser we dont know because we are yet to assume all catchable lobsters are caught, so why does this assumption matters??

And if we dont assume this and the population of lobster declined significantly, why cant we still assume the illegal party still was able to catch 9000?

For example if there were 100,000 lobster in 1996 and in 1992 declined significantly to 30,000, the number of the lobster caught by legal fishers would have been decreasing over the years which is in line with the story and 9000 less in 1996. So may be from 20000 to 11,000. There are still 19000 catchable lobsters left so it’s still possible that the illegal fishers caught the 9,000 instead. Unless if choice A states that the remaining catchable lobster is significantly lowered to below 9000+number they caught in 1996, then i dont see how negating this option really destroy conclusion.

In my view if it’s significantly lowered then all the more reason both fishers were able to caught all catchable lobsters which would make sense how they know how many the other party got.
bestreturn

Looking at your doubt, I can see why this logic feels confusing - you're actually thinking more deeply than the argument requires, which is causing the confusion. Let me help clarify the core logical mechanism at play here.

The Key Insight You're Missing:

You're absolutely right that we don't know if "all catchable lobsters are caught" - and that's exactly why the argument needs assumption (A). The argument is making a causal claim: the 9,000-ton shortfall in legal catch was caused by illegal boats taking those 9,000 tons.

Why Your Reasoning Actually Supports Choice (A):

Your example perfectly illustrates the problem! You said:
"If there were 100,000 lobsters in 1992 and declined significantly to 30,000 in 1996..."

This is exactly what assumption (A) is ruling out. If the population crashed from 100,000 to 30,000, then:
  • The 9,000-ton shortfall in legal catch could be because there are fewer lobsters to catch
  • We can't conclude that illegal boats caught exactly 9,000 tons
  • Maybe illegal boats caught 15,000 tons, or 5,000 tons - we have no way to know!

The Logic Structure:

The argument needs to establish: Legal shortfall = Illegal catch

For this equation to work, we must assume the total pie didn't shrink. If the pie (lobster population) stayed roughly the same, then what legal fishers lost (9,000 tons) = what illegal fishers gained.

Process Diagnosis:
You got stuck because you were trying to track absolute numbers of lobsters rather than focusing on the cause of the shortfall. GMAT assumption questions often test whether you can identify what alternative explanation needs to be ruled out.

Strategic Framework for Assumption Questions:

When you see a causal argument (X caused Y), always ask: "What else could have caused Y?"
  1. Identify the claimed cause-effect relationship
  2. List alternative explanations for the effect
  3. The correct assumption will rule out a major alternative

In this case:
- Claimed cause: Illegal fishing caused the 9,000-ton shortfall
- Alternative explanation: Population decline caused the shortfall
- Assumption needed: Rule out population decline (Choice A)

If you'd like, you can practice similar questions here- you'll find a lot of OG questions as well as the detailed framework to approach similar CR questions.
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Passage Analysis

In 1992 outlaw fishing boats began illegally harvesting lobsters from the territorial waters of the country of Belukia.

The statement talks about outlaw fishing boats, which means illegal fishing boats. These boats started illegal harvesting of lobsters from the waters of the country of Belukia in 1992.

Soon after, the annual tonnage of lobster legally harvested in Belukian waters began declining;

Soon after that illegal harvesting of lobster started, the amount of lobster legally harvested in Belukian waters started to decline. Given that two events are happening so close to each other, it seems that the first, which is the beginning of illegal harvesting of lobsters, is the cause of the decline in the amount of lobsters legally harvested. This is not stated directly, but if you try to connect the two statements, that seems to be a possible connection.

in 1996, despite there being no reduction in the level of legal lobster fishing activity, the local catch was 9,000 tons below pre-1992 levels.

The statement talks about 1996 and it presents a contrast. The first element of the contrast is that there was no reduction in the level of legal lobster fishing activity. So, the amount of effort being spent to legally harvest lobster is the same as it was before 1992, but still, the local catch of lobster was 9,000 tons below pre-1992 levels. The contrast is that we are still making the same effort to catch lobster, but we are catching a smaller amount of lobster. Connecting it to the previous sentences, we can understand that this reduction could be the result of the illegal harvesting of lobster.

It is therefore highly likely that the outlaw fishing boats harvested about 9,000 tons of lobster illegally that year.

This statement is a conclusion. It says that it is very likely that illegal fishing boats harvested about 9,000 tons of lobsters illegally in 1996. How do we arrive at this conclusion? Because the amount of legally harvested lobster has come down by 9,000 tons, and that reduction is not caused by any decrease in the level of legal harvesting. There must be some other cause, and the cause that we are thinking of is that of illegal harvesting. So, we are saying the entire deficit must be accounted for by the illegal harvesting of lobster by those outlaw fishing boats.

Let's try to think about it. The argument rules out one potential cause of the reduction in the legal catch of lobsters: the argument rules out any decrease in the activity of legal harvesting. The argument then concludes that the cause of the reduction is entirely illegal harvesting. Can there be another cause for the reduction in the harvesting of lobsters?

Well, I can think of a couple of possible options. One is that the total number of lobsters available might have come down by 1996. So, it's not that the same amount of lobster can be harvested with the same amount of activity because there are now fewer lobsters available. This can account for the reduction in the harvesting of legal lobster in 1996.

Another possible cause that I can think of is that lobsters have become really adept at avoiding being caught. So if you make the same amount of effort, you are able to catch fewer lobsters because they are really good at avoiding being caught. This could also explain why the amount of legally harvested lobster has come down in 1996. In such cases, we won't be able to say that the amount of illegal harvesting was about 9,000 tons in 1996.

Deconstructing the Question

Which of the following is an assumption on which the argument depends?

We are looking for an assumption here. An assumption is something that is needed for the argument to hold, so if you negate the assumption, the argument has to break down. That is how you figure out whether an option is an assumption or not.

We also know that every assumption has to be a strengthener, because why would an author assume something that is not even supporting his argument? So if an option is not even strengthening the argument, it can be ruled out.

If an option is strengthening, then we have to negate it and see whether negating it breaks down the argument. Only then can we be sure that it is an assumption.

There are a couple of ways to rule out options: options that are not even strengtheners can be ruled out, or options whose negation doesn't break down the argument can also be ruled out.

Options Evaluation

(A) The illegal lobster harvesting was not so extensive that the population of catchable lobsters in Belukia's territorial waters had sharply declined by 1996.

Correct. This option says that illegal lobster harvesting was not so high that the population of catchable lobsters in the relevant waters had declined sharply by 1996. So this option is talking about the amount of illegal lobster harvesting before 1996 and saying that this illegal harvesting was not so high that the population of catchable lobsters had declined sharply by 1996. This is a negative statement: it has a 'not' in it. Negative statements are usually more difficult to understand than positive statements. Anything that is more difficult to understand is also more difficult to evaluate, so let's look at the negation directly, and then we'll see the impact of that.

Negation: The illegal lobster harvesting was so extensive that the population of catchable lobsters in Belukia's territorial waters had sharply declined by 1996.

The negation of this option means that the illegal harvesting before 1996 was so high that the amount of catchable lobster had sharply declined by 1996. If the amount of catchable lobster declined by 1996, that could explain why the amount of legal harvesting of lobsters was less in 1996. In that case, you can't say that the amount of illegal harvesting of lobster in 1996 was 9,000 tons. In that case, the amount of illegal harvesting of lobsters could be much less than 9,000 or maybe even zero, depending upon how much the amount of catchable lobster had declined by 1996. So we can see that the negation of this option breaks down the argument, so this option is an assumption.

(B) The average annual lobster catch, in tons, of an outlaw fishing boat has increased steadily since 1992.

Incorrect. This option talks about the trend in the average amount of annual lobster catch by outlaw fishing boats. So essentially, this option is talking about the amount of lobster catch per boat and it's saying that that average has steadily increased from 1992 to 1996. This option has no impact on the argument. Whether this average is increasing, decreasing, or staying the same, the argument remains the same: that given the amount of legal harvesting of lobster has gone down, the amount of illegal lobster harvesting should account for that reduction.

(C) Outlaw fishing boats do not, as a group, harvest more lobsters than do licensed lobster-fishing boats.

Incorrect. This option is comparing the number of lobsters harvested between outlaw fishing boats and licensed legal fishing boats. This option is saying that illegal fishing boats do not harvest more lobsters than legal fishing boats. This option also has no impact on the argument because irrespective of this comparison—whether it's more, less, or the same—the argument is not impacted.

(D) The annual legal lobster harvest in Belukia in 1996 was not significantly less than 9,000 tons.

Incorrect. This option is talking about the amount of legal lobster harvest in 1996, and it's saying that it was not significantly less than 9,000 tons. Think about it. Whether the legal harvest is 6,000 tons or 60,000 tons, we know as a fact that it is 9,000 tons less than it was before 1992. So the whole argument still remains the same: that that 9,000 tons must be accounted for by illegal lobster harvesting, irrespective of whether the legal harvest is 6,000 tons in 1996 or 60,000 tons.

(E) A significant proportion of Belukia's operators of licensed lobster-fishing boats went out of business between 1992 and 1996.

Incorrect. This option is talking about the proportion of operators of legal fishing boats that went out of business between 1992 and 1996. If we had not been given that the amount of legal lobster fishing activity has remained the same, this option would have indicated a reduction in the amount of that activity. In that case, this option would have presented an alternate cause and weakened the argument. However, we are already given in the argument that the amount of legal lobster fishing activity has remained the same. So the number or the proportion of operators of fishing boats going out of business is irrelevant to the argument.
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Premise - In 1992 outlaw fishing boats began illegally harvesting lobsters from the territorial waters of the country of Belukia. Soon after, the annual tonnage of lobster legally harvested in Belukian waters began declining; in 1996, despite there being no reduction in the level of legal lobster fishing activity, the local catch was 9,000 tons below pre-1992 levels.

Conclusion - It is therefore highly likely that the outlaw fishing boats harvested about 9,000 tons of lobster illegally that year.

Gap Analysis

1) Population collapse - Maybe the illegal fishing in 1996 could have been only 1000 tons but the overall population of lobster could have collapsed due to previous activities. Basically the overall available population could have been less than 9000 tons.

2) Predators of lobsters could be thriving in these territorial waters leading to these reduced numbers.

3) Similarly other factors such as spreading of some virus or disease or a direct decrease in water quality could have led to reduced catch in 1996.

Which of the following is an assumption on which the argument depends?


(A) The illegal lobster harvesting was not so extensive that the population of catchable lobsters in Belukia’s territorial waters had sharply declined by 1996.

- The negation of this option relates to gap 1 directly. Because if the population was so less than in 1996 the outlaw boats simply migh have caught much less numbers than 9000 tons

(B) The average annual lobster catch, in tons, of an outlaw fishing boat has increased steadily since 1992.

- Even if the annual average lobster catch did reduce each year, the conclusion still might stand as the levels could have reduced to 9000.

(C) Outlaw fishing boats do not, as a group, harvest more lobsters than do licensed lobster-fishing boats.

- The negation doesn’t destroy the argument, it just says that outlaw groups harvested more than legal fishing group.

(D) The annual legal lobster harvest in Belukia in 1996 was not significantly less than 9,000 tons.

- Zero Impact as legal harvest could have been 9000 more in the previous year.

(E) A significant proportion of Belukia’s operators of licensed lobster-fishing boats went out of business between 1992 and 1996.

- Negation strenghtens the argument as it plugs a potential explanation.
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