Photograph courtesy Zeb Hogan
Tourists walk past a preserved paddlefish on display at the Yangtze River Fishery Research Institute in Jingzhou, China. This critically endangered species lives in China's Yangtze River and is a contender for largest freshwater fish in the world. Unfortunately, overfishing and dam construction have decimated paddlefish populations. None have been seen in the wild since 2003, and scientists worry the species may already be extinct.