Fish

Fish were the first vertebrates to appear on Earth, and today they remain the most diverse group of vertebrate animals, with tens of thousands of species inhabiting oceans, rivers, lakes, and coral reefs worldwide. Breathing through gills and typically covered in scales, fish have adapted to nearly every aquatic environment on the planet, from the crushing pressure of the deep sea to shallow freshwater streams.

The diversity within this group is staggering. Predators like the bull shark and blue marlin patrol open water with speed and power, while reef fish such as the blue tang rely on color and agility to survive among coral. Freshwater species like the koi carp have been bred for centuries for their beauty, and bizarre deep-sea dwellers such as the anglerfish and blobfish have evolved extraordinary adaptations to survive where sunlight never reaches.

Below you'll find detailed profiles covering the habitat, diet, behavior, and conservation status of fish species from across the world's waters. Each entry includes physical characteristics and taxonomy, along with answers to the questions people ask most — from what these fish eat to how long they live.