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Amazon dolphin numbers threatened by proposed dams and dredging


Scientists used satellite tags to track eight dolphins in the Peruvian Amazon, revealing the risks that proposed dams and dredging sites could pose for the marine mammals.

Amazon river dolphins are under threat from fishing and proposed new dams and dredging, research shows.

Through the satellite tags, the team at the University of Exeter and Peruvian conservation organisation Pro Delphinus found that 89 per cent of the area the dolphins live in is currently being used for fishing.

“It’s clear that the Amazon river dolphin is facing increasing threats from humans,” said Dr Elizabeth Campbell, a researcher on the study. “Fishing can deplete populations of the dolphins’ prey, and dolphins are also at risk from intentional killing and bycatch (accidental catching).

“Bycatch has been known to be a threat to these dolphins for the last 30 years, but there’s no real data on how many dolphins are caught per year.”

In the research, the river dolphins were found to be an average of 252km from the nearest proposed dam and 125km from the nearest proposed dredging site. Although this distance might seem significant, their mobility range spans over 50km on average, and dams and dredging can affect large stretches of river habitats.

Additionally, many Amazon river dolphins – already an endangered species – live closer to the proposed sites than the seven males and one female tagged in this study.

Amazon river dolphins

Amazon river dolphins / Jose Luis Mena

Image credit: Jose Luis Mena

The construction of dams, mainly in Brazil, is an expanding threat to the dolphins’ lives, with 175 dams operating or under construction in the Amazon basin, and at least 428 more planned over the next 30 years.

Additionally, the Amazon Waterway has been approved and is under contract for construction. This project will involve dredging sites across four main rivers of the Amazon basin, and the expansion of ports to facilitate ship navigation across the Amazon, Ucayali and Marañón rivers.

Despite these challenges, the researchers say the Peruvian government still has an opportunity to protect this endangered species.

“Peru has a chance to preserve its free-flowing rivers, keeping them a safe and healthy habitat for river dolphins and many other species,” Dr Campbell said. “Given that many of these dams and dredging projects are still in the planning stage, we advise the government to consider the negative effects these activities have already had on river species elsewhere.”

The researchers recommended that the government expands river dolphin tracking programmes to span multiple seasons, track more females at study sites and increase the numbers tracked in other areas to improve knowledge of their movement patterns.

The study’s findings were published in the journal Oryx.

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