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UPSC Prelims 2014 · Environment · Species Watch
Other than poaching, what are the possible reasons for the decline in the population of Ganges River Dolphins? Select the correct answer using the code given below.
- Construction of dams and barrages on rivers
- Increase in the population of crocodiles in rivers
- Getting trapped in fishing nets accidentally
- Use of synthetic fertilizers and other agricultural chemicals in crop-fields in the vicinity of rivers.
- (a) 1 and 2 only
- (b) 2 and 3 only
- (c) 1, 3 and 4 only
- (d) 1, 2, 3 and 4
Show the answer and explanation
Answer: (c) 1, 3 and 4 only
Dams, nets and farm chemicals all harm river dolphins.
Statement by statement
1. ✓ YES Dams and barrages cut rivers into isolated pieces and reduce the flow dolphins need.
2. ✗ NO Crocodiles are not a major threat, and their numbers have not risen much.
3. ✓ YES Dolphins get tangled in gill nets and drown.
4. ✓ YES Fertiliser and pesticide run-off pollutes the river and their prey.
The idea
A river dolphin needs a river that is connected from end to end, deep even in the dry season, and clean enough for fish. Each human use of the river breaks one of these conditions.
Dams and barrages → river cut into pieces, less water downstream → Fishing nets → dolphins get tangled and drown → Farm chemicals and sewage → fewer fish, poisoned water → Sand mining and boat traffic → noise and loss of deep pools
The trap
Predators feel like a natural reason. The real threats are human.
Also know
Dolphins were also killed for their oil, used as bait for catfish. A close relative, the Indus dolphin, survives in India only in the Beas river in Punjab.
🔒 River dolphin threats: dams/barrages, fishing nets, pollution, sand mining, oil poaching. Project Dolphin 2020.