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.
- (a) 1 and 2 only
- (b) 2 and 3 only
- (c) 1, 3 and 4 only ✓ UPSC's answer
- (d) 1, 2, 3 and 4
Why the answer is (c)
• Dams and barrages (1) fragment dolphin populations, block migration and alter flows and prey.
• Accidental entanglement in gillnets (3) is a leading cause of death.
• Fertiliser and pesticide run-off (4) pollutes rivers and bioaccumulates in the dolphins, which sit at the top of the food chain.
• Crocodiles (2) coexisted with dolphins for millennia and are not a cause of decline.
• Hence 1, 3 and 4 only, option (c).
Why the other options are wrong
- (a) 1 and 2 only
- Crocodiles are not a cause; fishing nets and chemicals are.
- (b) 2 and 3 only
- Crocodiles are not a cause; dams and chemicals are.
- (d) 1, 2, 3 and 4
- Crocodile numbers are not a cause of dolphin decline.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2014, held on 24 August 2014. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.