Many populations of Atlantic salmon are in decline and are listed as threatened under the Endangered Species Act. (Robert F. Bukaty and Jason Leighton / Associated Press)
A female manatee and her calf in the Crystal River in Florida. Manatees are considered endangered. (Rick Loomis / Los Angeles Times)
The polar bear is classified as a threatened species. Global warming is now seen as the bear’s most significant threat. (Paul J. Richards / AFP/Getty Images)
