Meet the red handfish, the critically endangered fish that walks

For 20 years, photographer Joel Sartore has been documenting animals through his Photo Ark project, which has now reached its 18,000th species. The latest addition is the critically endangered red handfish, a tiny marine fish that uses its fins to move across the seafloor. Sartore hopes the project will raise awareness about threatened species and help preserve a record of animals that could disappear.