An oarfish, also known as a "doomsday fish," was spotted on Grandview Beach in Encinitas, California by a PhD candidate at Scripps Oceanography who recognized the species.

The Devils Hole pupfish are the rarest fish in the world. Last year, scientists counted just 175 of them swimming in a deep cavernous pool in the Death Valley National Park in Nevada.

The asprete, a ray-finned freshwater fish species that lives only in Romania, has long captured Mircea Marginean’s imagination. He remembers hearing about the species in 2011, when he was a ...