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. Construction of dams and barrages on rivers — Correct. These fragment river habitat, alter flow, and isolate dolphin populations, which is a known cause of decline.

2. Increase in the population of crocodiles in rivers — Incorrect. This is not recognized as a major reason for the decline of Ganges River Dolphins in standard conservation literature.

3. Getting trapped in fishing nets accidentally — Correct. Accidental entanglement/bycatch in fishing gear is a significant threat to river dolphins.

4. Use of synthetic fertilizers and other agricultural chemicals in crop-fields near rivers — Correct. Agricultural runoff pollutes river water and degrades habitat, affecting dolphin survival.

Therefore, 1, 3 and 4 only are correct.