South American River Dolphin Census Results
Freshwater Dolphins Counted in Thirteen Rivers in Five Countries
Oct 20, 2008
In the course of two years 3188 river dolphins were counted and those numbers are encouraging. But the river dolphin survey is just the first step in the efforts to protect South America’s freshwater cetaceans. The organizations involved will now look at developing a conservation strategy for the river dolphins.
The World Wildlife Fund, the Wildlife Conservation Society (WCS) and the Whale and Dolphin Conservation Society partnered with South American NGOs such as the Omacha Foundation, the LaSalle Foundation and Faunagua in conducting this river dolphin survey. The governments of Bolivia, Brazil, Columbia, Ecuador, Peru and Venezuela were involved as well.
The River Dolphins of South America
The Amazon or pink river dolphin (Inia geoffrensis) and the tucuxi or gray river dolphin (Sotalia fluviatilis) are the two species found in South American rivers. The pink river dolphin is endangered but not much was known about the numbers of tucuxi so the survey results will help the IUCN determine their status as they are now listed as Data Deficient.
The gray river dolphin is not strictly a freshwater species. There are two separate populations (they may actually be separate species), one of which is found in the Amazon basin and the other which inhabits shallow coastal waters and estuaries.
What the River Dolphin Survey Found
Seven expeditions were needed to complete the survey. In the process a new method of census was developed and is now certified by the International Union for the Conservation of Nature (IUCN). This will help standardize the way some aquatic mammal populations are surveyed so that results can be compared and there is consistency in the data produced.
In addition to the actual numbers of freshwater dolphins counted, it was determined that the Amazon River basin populations were more stable than those in the Orinoco River basin. The researchers also found that the Amazon River dolphins had moved into different parts of the river basin. What this means in terms of the health of the habitat needs to be determined.
The Next Step: Developing a River Dolphin Conservation Strategy
The organizations involved in the survey are looking at an overall South American River dolphin conservation strategy. Early efforts are likely to focus on problems with the mota (Calophysus macropterus) fishery where river dolphins are used as bait as they are easily caught. The other fishery that is having an impact on freshwater dolphins is at Caballo Cocha in Peru. Here the dolphins have been damaging nets and the fish in them. Local fishermen have begun poisoning dolphins in response. Conservation organizations are looking at ways to mitigate these human-dolphin conflicts.
Ongoing monitoring of the South American river dolphins will also aid in improving the health of the Amazon and Orinoco river basins. Pollution and development threaten all the wildlife of these areas so a long term conservation strategy for the freshwater dolphins will likely have a positive impact on the entire ecosystem.
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