UPSC Prelims 2014 · Question 74 of 100

UPSC Prelims 2014 question on Ganges River Dolphin Decline

Other than poaching, what are the possible reasons for the decline in the population of Ganges River Dolphins?

1. Construction of dams and barrages on rivers

2. Increase in the population of crocodiles in rivers

3. Getting trapped in fishing nets accidentally

4. Use of synthetic fertilizers and other agricultural chemicals in crop-fields in the vicinity of rivers

Select the correct answer using the code given below.

  1. 1 and 2 only
  2. 2 and 3 only
  3. 1, 3 and 4 only
  4. 1, 2, 3 and 4
Show answer

Answer: C. 1, 3 and 4 only

Verdict

The answer is 1, 3 and 4 only. Dams, fishing net entanglement and agricultural chemicals all threaten the Ganges river dolphin, but crocodile numbers do not.

Analysis

Statement 1 is CORRECT. Dams and barrages fragment the river, isolate populations and alter flow and depth. Statement 3 is CORRECT. Accidental entanglement in gill nets is a leading direct cause of mortality. Statement 4 is CORRECT. Fertiliser and pesticide runoff degrades water quality and the prey base. Statement 2 is INCORRECT. Crocodiles are not a significant predator or competitor of the dolphin, and crocodile populations are not a documented driver of dolphin decline.

Source

WWF material on the Ganges river dolphin.

How to crack it

For any species decline question, the causes are almost always anthropogenic, that is habitat loss, fragmentation, bycatch, pollution and direct killing. A statement blaming another native species should stand out immediately as the odd one, because natural predator prey relationships are old and stable while the decline is recent. Fuse the static fact, that the Ganges river dolphin is India's national aquatic animal, with the news hook of river infrastructure debates, since that pairing is what keeps this species examinable.

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