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Difficulty: HardApplying the Negation Technique

Marine Biologist: The population of the reef-dwelling clown triggerfish has declined significantly over the past decade. Some conservationists attribute this to increased commercial fishing in the area. However, recent data shows that the population of predatory grouper, which primarily feed on juvenile clown triggerfish, has doubled during the same period. Since commercial fishing operations in this region primarily target tuna and completely ignore grouper, it is clear that the grouper population explosion, rather than commercial fishing, is responsible for the decline of the clown triggerfish.

Which of the following statements, if logically negated, would fatally undermine the marine biologist's conclusion? (Select all that apply)

  1. The methods used by commercial tuna fishers have not inadvertently eliminated the natural predators of the grouper.Answer
  2. The commercial fishing operations targeting tuna do not result in significant bycatch of clown triggerfish.Answer
  3. C
    Any significant increase in a predator population will lead to a decline in its primary prey.
  4. D
    The increased grouper population is capable of consuming the entire population of juvenile clown triggerfish in the reef.
  5. E
    There is no correlation between the areas of the reef most heavily fished by commercial vessels and the areas where the clown triggerfish decline is most severe.

Answer

The correct statements are the ones indicating that commercial tuna fishers have not eliminated the grouper's natural predators, and that commercial fishing operations do not result in significant bycatch of clown triggerfish.
The argument explicitly concludes that the grouper, rather than commercial fishing, is responsible for the decline. For this causal conclusion to hold, the author must assume that commercial fishing is not the hidden root cause of the grouper explosion itself, and that commercial fishing is not secretly depleting the triggerfish through untargeted bycatch. Negating these specific statements reveals scenarios where commercial fishing is ultimately to blame, thereby logically destroying the author's conclusion.

Step-by-Step Solution

1
Identify the argument's core structure.
Conclusion: Grouper, rather than commercial fishing, is responsible for the decline. Premises: Grouper population doubled and they eat triggerfish; commercial fishing targets tuna and ignores grouper.
Understanding the precise causal claim (A caused the problem, not B) is necessary before evaluating assumptions.
2
Apply the Negation Technique to each option.
Mentally reverse the logical meaning of each statement to see how it impacts the argument when proven false.
A necessary assumption is one that, if proven false, causes the argument's conclusion to collapse.
3
Evaluate the negated statements against the conclusion.
Negating the correct options shows scenarios where commercial fishing is either the direct cause (bycatch) or the indirect root cause (eliminating grouper predators). Both scenarios destroy the conclusion.
If commercial fishing is the true cause, the conclusion that it is 'rather than commercial fishing' is fatally undermined.

Key Concept

Applying the Negation Technique to Causal Assumptions
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Topics

Applying the Negation Technique

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