Fish Facts

Deep-dive facts about fish — the surprisingly complex lives of our underwater neighbors.

Fish represent the most species-rich group of vertebrates on Earth, comprising more than 33,000 described species — over half of all known vertebrate species. They occupy virtually every aquatic habitat on the planet, from the near-boiling waters adjacent to hydrothermal vents to subzero Antarctic seas, from deep-ocean trenches to high-altitude Himalayan lakes. Fish biology routinely produces verified facts that confound popular assumptions: many fish species have sophisticated long-term memory (the three-second myth has no scientific basis), some species change sex during their lifetimes as an adaptive strategy, and the lungfish of sub-Saharan Africa can survive years of complete drought encased in a mucus cocoon.