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...