Why Ganges River Dolphins Are Endangered

The endangered Ganges river dolphin is one of two distinct dolphins living in the rivers of South Asia. The species was first listed as endangered by the International Union for Conservation of Nature (IUCN) in 1996, and experts estimate that the global population has diminished by over 50% since 1957.

Before the construction of barrages and other major changes to their habitats in the 1950s, there was little information on the historical abundance of the Ganges river dolphin. In 2014, survey data showed a total population of about 3,500 individuals—down from between 4,000 and 5,000 in the early 1980s—while more recent studies from 2019 estimate between 4,450 and 5,670. The World Wildlife Fund puts current populations at between 3,500 and 5,000.

The IUCN maintains that these estimates are negatively biased and often don’t account for areas with potentially large numbers of subpopulations. One thing agreed upon, however, is that the remaining global population is severely fragmented. Data implies that the species’ current range throughout India, Nepal, and Bangladesh has declined progressively since the 19th century.

Threats

The Ganges river dolphin’s range lies within some of the Earth’s most densely populated areas. Typically, both fishermen and dolphins congregate in the same spots where nutrients are rich, currents slower, and fish concentrated.

Because of this intersection, Ganges river dolphins are mainly threatened by human activities such as pollution, bycatch, and infrastructure, but also suffer similar consequences of climate change as other marine mammals.

Climate Change

The effects of climate change have impacted the Ganges dolphin by driving more saltwater into their river habitats. A 2018 study in the Journal of Threatened Taxa found that the freshwater dolphins were disappearing from the Sundarbans delta, which connects India with neighboring Bangladesh, due to a reduction in freshwater flow and increased salinity.

By examining boat and land surveys and interviewing local fishers and boaters, the study’s authors concluded that salinity has increased over the past few decades because of climate-induced glacial melting and sea-level rise.

Pollution

Since the river ecosystems that make up the Ganges dolphin’s range are in close proximity to human activities, they are especially susceptible to sewage and industrial wastewater, chemical pollution from agriculture or mining, and noise pollution from underwater explosions and vessels. Studies show that around 2 billion liters of untreated human waste from five separate states enter the Ganges every day.

The presence of pharmaceutical and personal care products (PPCPs) in the Ganges region has been associated with a higher risk of algal blooms and adverse health effects on river fish, which the dolphins need to survive. In 2021, researchers in India identified 15 different PPCPs in the Ganges, including caffeine, anti-inflammatory drugs, antibiotics, beta-blockers, antibacterials, and insect repellents. The research team also found that the toxic contaminant levels could potentially bioaccumulate in organisms like the dolphins themselves but also cause microbes in the waters to become resistant to the drugs.

Ganges river dolphins are almost entirely blind, relying on echolocation clicks to assess and search their surroundings. Modern technology has made way for more underwater noise pollution from motorized vessels in dolphin habitats, which has been shown to suppress the animals’ activity. During chronic exposure to ambient noise levels, dolphins completely alter their acoustic responses, and their metabolic stress can more than double.

Fishery Bycatch

Although the number of Ganges dolphins killed deliberately for their meat and oil is believed to have declined since the enactment of the Indian Wildlife Protection Act in 1972, incidental mortality from fishing gears (especially gillnets) remains a severe threat throughout the dolphin’s range. Despite the law, however, it’s not uncommon for fishers to place nets in areas where they are more likely to “accidentally” catch dolphins; This process is known as “assisted incidental capture.”

Dams and Barrages

Dams and low-gate barrages restrict dolphin movement, which in turn isolates them into smaller subpopulations with low genetic diversity. The Farakka Barrage, for example, spans the entire width of the Ganga River and controls water flow through several sluice gates. The barrage has affected the dolphin population in the Ganges by creating a physical barrier for movement, but also by changing the reach of the river from a lotic (rapidly moving freshwater) to a lentic (still freshwater) ecosystem.

What We Can Do

Rivers are delicate ecosystems that are already at risk from stressors like habitat loss, changes in water quality, natural resource exploitation, climate change, invasive species, and pollution. As top predators, Ganges river dolphins also have an important role as ecological indicators. Their presence or absence in a region can help indicate ecosystem transformations and aid in conservation efforts. At the same time, maintaining viable freshwater dolphin populations will require the management of entire ecosystems.

How can this be achieved? Experts have suggested everything from developing community-based dolphin conservation areas and promoting sustainable fisheries to implementing ecotourism projects focused on dolphins that protect against disturbance or harassment. Raising awareness on the international and local levels with media campaigns and innovative information centers may also help.

To combat assisted incidental capture, for instance, local conservationists have created outreach programs to educate fishers on alternatives to dolphin oil used for fish bait. They’ve found that oil made from fish scraps has a similar effect.

The National Marine Mammal Foundation (NMMF) has teams working in India that locate and free trapped dolphins. According to the nonprofit, some years see as many as ten dolphins rescued and returned to their river habitats. The program also offers opportunities for biologists to gather data on the health and reproductive status of the species.

In the future, the NMMF will also be providing training in veterinary skills, health assessment, and sample analysis to local researchers.