Freshwater dolphin survey starts

Scientists in South America have started the first studied of the continent's freshwater dolphins.

A team of dolphin experts from Peru, Colombia, Bolivia and Venezuela are travelling from the Venezuelan city of Ciudad Bolivar 1075 miles/1730km upriver to Puerto Carreno in Colombia to assess the scale of the dolphin population.

The population of freshwater dolphins is believed to have fallen, primarily due to mercury poisoning caused by the gold mining industry, and the mammals are listed as threatened on the IUCN Redlist.

Expedition leader, Fernando Trujillo, the Director of Fundacion Omacho told the WWF: "Freshwater dolphins are one of the most endangered mammals in the world. Mercury contamination, deforestation, indiscriminate capture and incidental fishing are some of the factors affecting the species.

"Currently we don't have abundant populations and this census will allow us to gather data in order to design a management and monitoring plan as well as get to know the state of the watersheds of the Amazon and Orinoco Rivers."

Several species of freshwater dolphin have been described from South America to date, the two most commonly seen are the Pink river dolphin or Boto, Inia geoffrensis, and the smaller porpoise-like Tucuxi, Sotalia fluviatilis.

The experts plan to travel upriver and plot the positions of dolphins using a GPS, as well as recording details on the size of the mammals and the habitats in which they were found.