The Amazon river dolphin faces new threats because its meat is used as bait to catch a popular catfish.The fish-like mammal is considered intelligent and friendly.The animal is known as the pink dolphin because its skin turns from gray to pink as it ages or when it gets excited.But some wildlife activists are concerned about new threats facing the world's largest freshwater dolphin.Brazilian fishermen hunt and kill the animals illegally to make bait for a catfish called the piracatinga.A temporary, legal ban on fishing for piracatinga ended last month.Since then, environmentalists and researchers have called for the ban to be restarted to help save Amazon river dolphins.One supporter of bringing the fishing ban back is biologist Vera da Silva.She has been working to protect Amazon river dolphins for the past 25 years.Silva told Reuters news agency that she and her team catch dolphins to examine, measure and mark them.The animals are then released into the Mamirauá Sustainable Development Reserve in northern Brazil.Such wildlife areas are established to protect land and animals in places where traditional populations live.The Mamirauá reserve covers about 11,000-square kilometers of flooded rainforest and wetlands."We captured a dolphin mother and her calf today and saw them calling out to each other," Silva said."They have a very strong relation until the calf becomes independent after three years."After being brought to a floating research center in the reserve, Silva's team takes blood and milk samples from the dolphins.A pregnancy usually lasts about 13 months.The mother then feeds her calf underwater for two years.Because of this extended feeding period, females only reproduce every three to five years.Silva says this low reproduction rate increases the risk of extinctionwhen the population of the Amazon river dolphins suffers major drops.Legal officials in Brazil's Amazonas state sought the catfish ban in 2015.At the time, they warned that as many as 2,500 dolphins were being killed each year for bait.Currently, Amazon river dolphins can still be found in large numbersacross South America's huge Amazon and Orinoco river basins.But Silva says she fears the animals could disappear like the Yangtze river dolphin didin China in 2006, after years of overfishing and pollution."We don't want the dolphins to become just a legend of Amazonia," she said.