With over 32,000 described fish species, the varieties are endless. Most bony fishes are cold-blooded, covered in scales and breathe using gills—but there are exceptions to all of these rules.  


X-ray image of a winghead shark


X-Rays of Fish Reveal Diversity

Scientists in the Division of Fishes at the Smithsonian's National Museum of Natural History use X-ray imaging to study the...
Photo of the head of a leafy seadragon

Devoted Dads: From Seahorses to Sea Spiders

Male leafy seadragons ( Phycodurus eques ) are among the ocean's more " devoted dads ." They carry the developing eggs for about a month, until they hatch. Credit: David Gray, FishWise Professional If...

Ocean Fish Pictures

Everyone knows what a fish is: from a pet goldfish to a wild sunfish, fish are globally recognized and are an important global protein source. In this slideshow, we will look at some of...