Grand challenges at the frontiers of fish science

It is common knowledge that fishes are the most speciose of the vertebrates with the true bony fishes, the teleosts, having over 34,000 species and still counting. Fishes thrive in water bodies over the entire globe, from polar seawaters at sub-zero temperatures to continental soda springs at 40◦C, and a huge diversity of aquatic habitats in between. They include species with extremely short life cycles, such as the azure killifish (Notobranchus furzeri) that inhabits seasonal puddles in equatorial Africa (1), and also the vertebrate with the longest known life span, the Greenland shark (Somniosus microcephalus) that lives in deep cold waters of the Northern Atlantic (2). The biology of fishes is so diverse and such a vast topic that each fish biologist may have their own opinion about what constitute the most interesting characteristics of fishes and the most important priorities for research