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A recent study conducted by Brazilian researchers has warned that freshwater dolphins found in the Amazon River Basin are “dying off fast”, and may face extinction unless they are more vigorously protected against fishing.
The report, published in the journal PLOS ONE, said that the “boto” (Inia geoffrensis) and the “tucuxi” (Sotalia fluviatilis), which were once considered abundant in the Amazon basin, are now halving in population every 10 years.
The primary reason for the decrease in numbers is the dolphins’ use of flesh and blubber as bait for catfish, which have become widely available commercially. Killing the dolphins endangers their survival, particularly since the females bear a single calf on average every four to five years.
Conducted by researcher Vera da Silva and her colleagues from the Instituto Nacional de Pesquisas da Amazonia in Manaus, Brazil, the research is based on their findings on 22 years of surveys in the Mamiraua Reserve in Brazil—an area described as a core part of their range—where dolphins have been tracked by boat monthly from 1994 to 2017.
The report noted that the rate of decline of the dolphins “was among the most severe of any measured in a cetacean (comprising of whales, dolphins and porpoises) population since the early years of modern whaling”.
The International Union for Conservation of Nature (IUCN) currently lists these freshwater dolphins’ status as "data deficient," meaning not enough is known about their numbers in the wild to assess the degree of threat to the population. But the study says that if the IUCN Red List considered the latest findings, both species would be classified as “Critically Endangered”.
The researchers called for greater enforcement of laws to protect the Amazon’s river dolphins.
Freshwater dolphins in other parts of the world are also facing extreme pressures. In the Indian Subcontinent, the Gangetic or Indus River Dolphin (Platanista gangetica) found in the Ganga and Indus River Basins is considered “Endangered” by the IUCN. In China, the Yangtze River dolphin or “baiji” (Lipotes vexillifer), was declared functionally extinct in 2006 due to human activities like overfishing, dam building, pollution and boat traffic.