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.

Correct Option The Ganges River Dolphin (Platanista gangetica) faces multiple anthropogenic threats leading to its population decline, besides poaching. - 1. Construction of dams and barrages on rivers: These structures impede the free movement of dolphins, fragment their habitats, and disrupt their migration routes and breeding grounds. This isolation can lead to genetic bottlenecks and reduced population viability. - 3. Getting trapped in fishing nets accidentally: Dolphins, needing to surface for air, often get entangled in various types of fishing nets, particularly gillnets, leading to accidental drowning. This bycatch is a significant cause of mortality. - 4. Use of synthetic fertilizers and other agricultural chemicals in crop-fields in the vicinity of rivers: Runoff from agricultural fields carries pesticides, herbicides, and excessive nutrients into rivers. This pollution degrades water quality, reduces the availability of prey species (like fish), and can have direct toxic effects on dolphins and their reproductive health. Incorrect Options - 2. Increase in the population of crocodiles in rivers: There is no scientific evidence to suggest that an increase in crocodile populations poses a significant threat or is a primary reason for the decline in Ganges River Dolphin numbers. Their ecological niches generally do not involve substantial predation pressure on adult dolphins. - Option 1 is incorrect because it includes statement 2. - Option 2 is incorrect because it includes statement 2 and excludes statements 1 and 4, which are valid reasons. - Option 4 is incorrect because it includes statement 2.

IAS 2014 — Environment & Ecology Environment & Ecology

2014mcqmedium

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

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

Select the correct answer using the code given below.

Official previous-year question

Verified 2 Aug 2026.

Options

A1 and 2 only
B2 and 3 only
C1, 3 and 4 only
D1, 2, 3 and 4

Did you get this right?

Solution

Correct Option

The Ganges River Dolphin (Platanista gangetica) faces multiple anthropogenic threats leading to its population decline, besides poaching.

1. Construction of dams and barrages on rivers: These structures impede the free movement of dolphins, fragment their habitats, and disrupt their migration routes and breeding grounds. This isolation can lead to genetic bottlenecks and reduced population viability.
3. Getting trapped in fishing nets accidentally: Dolphins, needing to surface for air, often get entangled in various types of fishing nets, particularly gillnets, leading to accidental drowning. This bycatch is a significant cause of mortality.
4. Use of synthetic fertilizers and other agricultural chemicals in crop-fields in the vicinity of rivers: Runoff from agricultural fields carries pesticides, herbicides, and excessive nutrients into rivers. This pollution degrades water quality, reduces the availability of prey species (like fish), and can have direct toxic effects on dolphins and their reproductive health.

Incorrect Options

2. Increase in the population of crocodiles in rivers: There is no scientific evidence to suggest that an increase in crocodile populations poses a significant threat or is a primary reason for the decline in Ganges River Dolphin numbers. Their ecological niches generally do not involve substantial predation pressure on adult dolphins.
Option 1 is incorrect because it includes statement 2.
Option 2 is incorrect because it includes statement 2 and excludes statements 1 and 4, which are valid reasons.
Option 4 is incorrect because it includes statement 2.

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Correct Option

The Ganges River Dolphin (Platanista gangetica) faces multiple anthropogenic threats leading to its population decline, besides poaching.

1. Construction of dams and barrages on rivers: These structures impede the free movement of dolphins, fragment their habitats, and disrupt their migration routes and breeding grounds. This isolation can lead to genetic bottlenecks and reduced population viability.
3. Getting trapped in fishing nets accidentally: Dolphins, needing to surface for air, often get entangled in various types of fishing nets, particularly gillnets, leading to accidental drowning. This bycatch is a significant cause of mortality.
4. Use of synthetic fertilizers and other agricultural chemicals in crop-fields in the vicinity of rivers: Runoff from agricultural fields carries pesticides, herbicides, and excessive nutrients into rivers. This pollution degrades water quality, reduces the availability of prey species (like fish), and can have direct toxic effects on dolphins and their reproductive health.

Incorrect Options

2. Increase in the population of crocodiles in rivers: There is no scientific evidence to suggest that an increase in crocodile populations poses a significant threat or is a primary reason for the decline in Ganges River Dolphin numbers. Their ecological niches generally do not involve substantial predation pressure on adult dolphins.
Option 1 is incorrect because it includes statement 2.
Option 2 is incorrect because it includes statement 2 and excludes statements 1 and 4, which are valid reasons.
Option 4 is incorrect because it includes statement 2.