• Fish have been on the earth for more than 450 million years, whereas mammals have only been on earth for roughly 200 million years
• There are over 27,000 identified species of fish on the earth and an estimated 15,000 fish species that have not yet been identified.
• There are more species of fish than all the species of amphibians, reptiles, birds and mammals combined.
• Sailfish, Swordfish, and Marlin are the fastest fish in the ocean, reaching speeds of up to 70 mph, which is faster than the speed limit on most highways!
• Goldfish can live for decades. The oldest known Goldfish, "Goldie," died in 2005 at 45 years of age. The second oldest Goldfish was "Tish" who died at 43.
• The largest fish in the world is the Whale Shark. The largest recorded Whale Shark was 12.6 m (41.5 ft) long, had a girth of 7 m (23 ft), and weighed more than 21,500 kg (47,300 lbs).
• Whale Sharks also lay the largest eggs of any animal. A Whale Shark egg measuring 35.6 cm (14 in) long was found in the Gulf of Mexico in the 1950s.
• The largest predatory Shark is the great White Shark. The largest one ever caught was 11.3 m (37 ft) long and weighted over 10,909 kg (24,000 lbs)
- The smallest fish is the tiny goby, which lives in the Philippines. It rarely grows longer than half an inch at adulthood, yet is so abundant it supports a fishery.
- Scientists can figure out how old a fish is by counting growth rings on its scales or its ear bones (called "otoliths"). The rings mark seasonal changes in fish growth, like the annual rings in tree trunks.
- A fish is an aquatic, anamniotic, gill-bearing vertebrate animal with swimming fins and a hard skull, but lacking limbs with digits. Fish can be grouped into the more basal jawless fish and the more common jawed fish, the latter including all living cartilaginous and bony fish, as well as the extinct placoderms and acanthodians. In a break from the long tradition of grouping all fish into a single class (''Pisces''), modern phylogenetics views fish as a paraphyletic group.