The number of freshwater pink dolphins has dropped 10 percent in Brazil's Amazon region over the past decade due to unrestrained killing, according to a report released Friday.

Nivia do Carmo, a researcher with the National Institute for Amazonian Research, said pink dolphins were slaughtered and used as fishing bait for piracatinga, a type of catfish heavily demanded in neighboring Colombia.

Therefore, fishing and selling piracatinga has become profitable for local people, he added.

Brazil's environmental police is drafting a strategy to fight illegal catch of wild fishes, and effective management is required in the Amazon basin.

The status of pink dolphins in the Amazon basin has been lifted from "a vulnerable species-threatened" to "an endangered species-threatened" recently by International Union for Conservation of Nature.